diff --git a/CHANGELOG.md b/CHANGELOG.md
index 38ea47e9..066829b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,10 @@
 # Changelog
 This file contains highlights of what changes on each version of the [Akismet for JS](https://github.com/cedx/akismet.js) library.
 
+## Version 9.1.0
+- Removed the dependency on [Babel](https://babeljs.io) compiler.
+- Updated the package dependencies.
+
 ## Version 9.0.0
 - Breaking change: reverted the API of the `Client` class to an [Observable](http://reactivex.io/intro.html)-based one.
 - Added new unit tests.
diff --git a/gulpfile.js b/gulpfile.js
index 09bb4de0..3a62e68d 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -4,22 +4,13 @@ const {david} = require('@cedx/gulp-david');
 const {spawn} = require('child_process');
 const del = require('del');
 const gulp = require('gulp');
-const babel = require('gulp-babel');
 const eslint = require('gulp-eslint');
 const {normalize} = require('path');
 
 /**
  * Runs the default tasks.
  */
-gulp.task('default', ['build']);
-
-/**
- * Builds the sources.
- */
-gulp.task('build', () => gulp.src('src/**/*.js')
-  .pipe(babel())
-  .pipe(gulp.dest('lib'))
-);
+gulp.task('default', ['lint']);
 
 /**
  * Deletes all generated files and reset any saved state.
@@ -49,7 +40,7 @@ gulp.task('doc', async () => {
 /**
  * Fixes the coding standards issues.
  */
-gulp.task('fix', () => gulp.src(['*.js', 'src/**/*.js', 'test/**/*.js'], {base: '.'})
+gulp.task('fix', () => gulp.src(['*.js', 'lib/**/*.js', 'test/**/*.js'], {base: '.'})
   .pipe(eslint({fix: true}))
   .pipe(gulp.dest('.'))
 );
@@ -57,7 +48,7 @@ gulp.task('fix', () => gulp.src(['*.js', 'src/**/*.js', 'test/**/*.js'], {base:
 /**
  * Performs static analysis of source code.
  */
-gulp.task('lint', () => gulp.src(['*.js', 'src/**/*.js', 'test/**/*.js'])
+gulp.task('lint', () => gulp.src(['*.js', 'lib/**/*.js', 'test/**/*.js'])
   .pipe(eslint())
   .pipe(eslint.format())
 );
@@ -69,7 +60,6 @@ gulp.task('test', () => _exec('node_modules/.bin/nyc', [
   '--report-dir=var',
   '--reporter=lcovonly',
   normalize('node_modules/.bin/mocha'),
-  '--compilers=js:babel-register',
   '--recursive'
 ]));
 
diff --git a/lib/author.js b/lib/author.js
new file mode 100644
index 00000000..bec3dc56
--- /dev/null
+++ b/lib/author.js
@@ -0,0 +1,94 @@
+'use strict';
+
+const {URL} = require('url');
+
+/**
+ * Represents the author of a comment.
+ */
+exports.Author = class Author {
+
+  /**
+   * Initializes a new instance of the class.
+   * @param {string} [ipAddress] The author's IP address.
+   * @param {string} [userAgent] The author's user agent.
+   */
+  constructor(ipAddress = '', userAgent = '') {
+
+    /**
+     * The author's mail address.
+     * @type {string}
+     */
+    this.email = '';
+
+    /**
+     * The author's IP address.
+     * @type {string}
+     */
+    this.ipAddress = ipAddress;
+
+    /**
+     * The author's name.
+     * @type {string}
+     */
+    this.name = '';
+
+    /**
+     * The role of the author.
+     * If you set it to `"administrator"`, Akismet will always return `false`.
+     * @type {string}
+     */
+    this.role = '';
+
+    /**
+     * The URL of the author's website.
+     * @type {URL}
+     */
+    this.url = null;
+
+    /**
+     * The author's user agent, that is the string identifying the Web browser used to submit comments.
+     * @type {string}
+     */
+    this.userAgent = userAgent;
+  }
+
+  /**
+   * Creates a new author from the specified JSON map.
+   * @param {object} map A JSON map representing an author.
+   * @return {Author} The instance corresponding to the specified JSON map, or `null` if a parsing error occurred.
+   */
+  static fromJSON(map) {
+    if (!map || typeof map != 'object') return null;
+
+    let author = new Author(typeof map.user_ip == 'string' ? map.user_ip : '');
+    author.email = typeof map.comment_author_email == 'string' ? map.comment_author_email : '';
+    author.name = typeof map.comment_author == 'string' ? map.comment_author : '';
+    author.role = typeof map.user_role == 'string' ? map.user_role : '';
+    author.url = typeof map.comment_author_url == 'string' ? new URL(map.comment_author_url) : null;
+    author.userAgent = typeof map.user_agent == 'string' ? map.user_agent : '';
+    return author;
+  }
+
+  /**
+   * Converts this object to a map in JSON format.
+   * @return {object} The map in JSON format corresponding to this object.
+   */
+  toJSON() {
+    let map = {};
+    if (this.name.length) map.comment_author = this.name;
+    if (this.email.length) map.comment_author_email = this.email;
+    if (this.url) map.comment_author_url = this.url.href;
+    if (this.userAgent.length) map.user_agent = this.userAgent;
+    if (this.ipAddress.length) map.user_ip = this.ipAddress;
+    if (this.role.length) map.user_role = this.role;
+    return map;
+  }
+
+  /**
+   * Returns a string representation of this object.
+   * @return {string} The string representation of this object.
+   */
+  toString() {
+    return `${this.constructor.name} ${JSON.stringify(this)}`;
+  }
+};
diff --git a/lib/blog.js b/lib/blog.js
new file mode 100644
index 00000000..1d6a28ff
--- /dev/null
+++ b/lib/blog.js
@@ -0,0 +1,70 @@
+'use strict';
+
+const {URL} = require('url');
+
+/**
+ * Represents the front page or home URL transmitted when making requests.
+ */
+exports.Blog = class Blog {
+
+  /**
+   * Initializes a new instance of the class.
+   * @param {string|URL} [url] The blog or site URL.
+   * @param {string} [charset] he character encoding for the values included in comments.
+   * @param {string[]} [languages] The languages in use on the blog or site, in ISO 639-1 format.
+   */
+  constructor(url = null, charset = '', languages = []) {
+
+    /**
+     * The character encoding for the values included in comments.
+     * @type {string}
+     */
+    this.charset = charset;
+
+    /**
+     * The languages in use on the blog or site, in ISO 639-1 format.
+     * @type {string[]}
+     */
+    this.languages = languages;
+
+    /**
+     * The blog or site URL.
+     * @type {URL}
+     */
+    this.url = typeof url == 'string' ? new URL(url) : url;
+  }
+
+  /**
+   * Creates a new blog from the specified JSON map.
+   * @param {object} map A JSON map representing a blog.
+   * @return {Blog} The instance corresponding to the specified JSON map, or `null` if a parsing error occurred.
+   */
+  static fromJSON(map) {
+    if (!map || typeof map != 'object') return null;
+
+    let blog = new Blog(typeof map.blog == 'string' ? map.blog : null);
+    blog.charset = typeof map.blog_charset == 'string' ? map.blog_charset : '';
+    blog.languages = typeof map.blog_lang == 'string' ? map.blog_lang.split(',').map(lang => lang.trim()).filter(lang => lang.length) : [];
+    return blog;
+  }
+
+  /**
+   * Converts this object to a map in JSON format.
+   * @return {object} The map in JSON format corresponding to this object.
+   */
+  toJSON() {
+    let map = {};
+    if (this.url) map.blog = this.url.href;
+    if (this.charset.length) map.blog_charset = this.charset;
+    if (this.languages.length) map.blog_lang = this.languages.join(',');
+    return map;
+  }
+
+  /**
+   * Returns a string representation of this object.
+   * @return {string} The string representation of this object.
+   */
+  toString() {
+    return `${this.constructor.name} ${JSON.stringify(this)}`;
+  }
+};
diff --git a/lib/client.js b/lib/client.js
new file mode 100644
index 00000000..24cf26a3
--- /dev/null
+++ b/lib/client.js
@@ -0,0 +1,190 @@
+'use strict';
+
+const {Observable, Subject} = require('rxjs');
+const superagent = require('superagent');
+const {URL} = require('url');
+
+const {Blog} = require('./blog');
+const {version: pkgVersion} = require('../package.json');
+
+/**
+ * Submits comments to the [Akismet](https://akismet.com) service.
+ */
+exports.Client = class Client {
+
+  /**
+   * The HTTP header containing the Akismet error messages.
+   * @type {string}
+   */
+  static get DEBUG_HEADER() {
+    return 'x-akismet-debug-help';
+  }
+
+  /**
+   * The URL of the default API end point.
+   * @type {URL}
+   */
+  static get DEFAULT_ENDPOINT() {
+    return new URL('https://rest.akismet.com');
+  }
+
+  /**
+   * Initializes a new instance of the class.
+   * @param {string} [apiKey] The Akismet API key.
+   * @param {Blog|string} [blog] The front page or home URL of the instance making requests.
+   */
+  constructor(apiKey = '', blog = null) {
+
+    /**
+     * The Akismet API key.
+     * @type {string}
+     */
+    this.apiKey = apiKey;
+
+    /**
+     * The front page or home URL of the instance making requests.
+     * @type {Blog}
+     */
+    this.blog = typeof blog == 'string' ? new Blog(blog) : blog;
+
+    /**
+     * The URL of the API end point.
+     * @type {URL}
+     */
+    this.endPoint = Client.DEFAULT_ENDPOINT;
+
+    /**
+     * Value indicating whether the client operates in test mode.
+     * You can use it when submitting test queries to Akismet.
+     * @type {boolean}
+     */
+    this.isTest = false;
+
+    /**
+     * The user agent string to use when making requests.
+     * If possible, the user agent string should always have the following format: `Application Name/Version | Plugin Name/Version`.
+     * @type {string}
+     */
+    this.userAgent = `Node.js/${process.version.substr(1)} | Akismet/${pkgVersion}`;
+
+    /**
+     * The handler of "request" events.
+     * @type {Subject<superagent.Request>}
+     */
+    this._onRequest = new Subject();
+
+    /**
+     * The handler of "response" events.
+     * @type {Subject<superagent.Response>}
+     */
+    this._onResponse = new Subject();
+  }
+
+  /**
+   * The stream of "request" events.
+   * @type {Observable<superagent.Request>}
+   */
+  get onRequest() {
+    return this._onRequest.asObservable();
+  }
+
+  /**
+   * The stream of "response" events.
+   * @type {Observable<superagent.Response>}
+   */
+  get onResponse() {
+    return this._onResponse.asObservable();
+  }
+
+  /**
+   * Checks the specified comment against the service database, and returns a value indicating whether it is spam.
+   * @param {Comment} comment The comment to be checked.
+   * @return {Observable<boolean>} A boolean value indicating whether it is spam.
+   */
+  checkComment(comment) {
+    let baseURL = `${this.endPoint.protocol}//${this.apiKey}.${this.endPoint.host}`;
+    let endPoint = new URL('1.1/comment-check', baseURL);
+    return this._fetch(endPoint, comment.toJSON()).map(res => res == 'true');
+  }
+
+  /**
+   * Submits the specified comment that was incorrectly marked as spam but should not have been.
+   * @param {Comment} comment The comment to be submitted.
+   * @return {Observable} Completes once the comment has been submitted.
+   */
+  submitHam(comment) {
+    let baseURL = `${this.endPoint.protocol}//${this.apiKey}.${this.endPoint.host}`;
+    let endPoint = new URL('1.1/submit-ham', baseURL);
+    return this._fetch(endPoint, comment.toJSON());
+  }
+
+  /**
+   * Submits the specified comment that was not marked as spam but should have been.
+   * @param {Comment} comment The comment to be submitted.
+   * @return {Observable} Completes once the comment has been submitted.
+   */
+  submitSpam(comment) {
+    let baseURL = `${this.endPoint.protocol}//${this.apiKey}.${this.endPoint.host}`;
+    let endPoint = new URL('1.1/submit-spam', baseURL);
+    return this._fetch(endPoint, comment.toJSON());
+  }
+
+  /**
+   * Converts this object to a map in JSON format.
+   * @return {object} The map in JSON format corresponding to this object.
+   */
+  toJSON() {
+    return {
+      apiKey: this.apiKey,
+      blog: this.blog ? this.blog.constructor.name : null,
+      endPoint: this.endPoint,
+      isTest: this.isTest,
+      userAgent: this.userAgent
+    };
+  }
+
+  /**
+   * Returns a string representation of this object.
+   * @return {string} The string representation of this object.
+   */
+  toString() {
+    return `${this.constructor.name} ${JSON.stringify(this)}`;
+  }
+
+  /**
+   * Checks the API key against the service database, and returns a value indicating whether it is valid.
+   * @return {Observable<boolean>} A boolean value indicating whether it is a valid API key.
+   */
+  verifyKey() {
+    let endPoint = new URL('1.1/verify-key', this.endPoint);
+    return this._fetch(endPoint, {key: this.apiKey}).map(res => res == 'valid');
+  }
+
+  /**
+   * Queries the service by posting the specified fields to a given end point, and returns the response as a string.
+   * @param {URL} endPoint The URL of the end point to query.
+   * @param {object} fields The fields describing the query body.
+   * @return {Observable<string>} The response as string.
+   * @emits {superagent.Request} The "request" event.
+   * @emits {superagent.Response} The "response" event.
+   */
+  _fetch(endPoint, fields) {
+    if (!this.apiKey.length || !this.blog) return Observable.throw(new Error('The API key or the blog URL is empty.'));
+
+    let bodyFields = Object.assign(this.blog.toJSON(), fields);
+    if (this.isTest) bodyFields.is_test = '1';
+
+    let req = superagent.post(endPoint.href)
+      .type('form')
+      .set('User-Agent', this.userAgent)
+      .send(bodyFields);
+
+    this._onRequest.next(req);
+    return Observable.from(req).map(res => {
+      this._onResponse.next(res);
+      if (!res.ok) throw new Error(`${res.status} ${res.statusText}`);
+      if (Client.DEBUG_HEADER in res.header) throw new Error(res.header[Client.DEBUG_HEADER]);
+      return res.text;
+    });
+  }
+};
diff --git a/lib/comment.js b/lib/comment.js
new file mode 100644
index 00000000..dc9222cb
--- /dev/null
+++ b/lib/comment.js
@@ -0,0 +1,107 @@
+'use strict';
+
+const {URL} = require('url');
+const {Author} = require('./author');
+
+/**
+ * Represents a comment submitted by an author.
+ */
+exports.Comment = class Comment {
+
+  /**
+   * Initializes a new instance of the class.
+   * @param {Author} [author] The comment's author.
+   * @param {string} [content] The comment's content.
+   * @param {string} [type] The comment's type.
+   */
+  constructor(author = null, content = '', type = '') {
+
+    /**
+     * The comment's author.
+     * @type {Author}
+     */
+    this.author = author;
+
+    /**
+     * The comment's content.
+     * @type {string}
+     */
+    this.content = content;
+
+    /**
+     * The UTC timestamp of the creation of the comment.
+     * @type {Date}
+     */
+    this.date = null;
+
+    /**
+     * The permanent location of the entry the comment is submitted to.
+     * @type {URL}
+     */
+    this.permalink = null;
+
+    /**
+     * The UTC timestamp of the publication time for the post, page or thread on which the comment was posted.
+     * @type {Date}
+     */
+    this.postModified = null;
+
+    /**
+     * The URL of the webpage that linked to the entry being requested.
+     * @type {URL}
+     */
+    this.referrer = null;
+
+    /**
+     * The comment's type.
+     * This string value specifies a `CommentType` constant or a made up value like `"registration"`.
+     * @type {string}
+     */
+    this.type = type;
+  }
+
+  /**
+   * Creates a new comment from the specified JSON map.
+   * @param {object} map A JSON map representing a comment.
+   * @return {Comment} The instance corresponding to the specified JSON map, or `null` if a parsing error occurred.
+   */
+  static fromJSON(map) {
+    if (!map || typeof map != 'object') return null;
+
+    let hasAuthor = Object.keys(map)
+      .filter(key => /^comment_author/.test(key) || /^user/.test(key))
+      .length > 0;
+
+    let comment = new Comment(hasAuthor ? Author.fromJSON(map) : null);
+    comment.content = typeof map.comment_content == 'string' ? map.comment_content : '';
+    comment.date = typeof map.comment_date_gmt == 'string' ? new Date(map.comment_date_gmt) : null;
+    comment.permalink = typeof map.permalink == 'string' ? new URL(map.permalink) : null;
+    comment.postModified = typeof map.comment_post_modified_gmt == 'string' ? new Date(map.comment_post_modified_gmt) : null;
+    comment.referrer = typeof map.referrer == 'string' ? new URL(map.referrer) : null;
+    comment.type = typeof map.comment_type == 'string' ? map.comment_type : '';
+    return comment;
+  }
+
+  /**
+   * Converts this object to a map in JSON format.
+   * @return {object} The map in JSON format corresponding to this object.
+   */
+  toJSON() {
+    let map = this.author ? this.author.toJSON() : {};
+    if (this.content.length) map.comment_content = this.content;
+    if (this.date) map.comment_date_gmt = this.date.toISOString();
+    if (this.postModified) map.comment_post_modified_gmt = this.postModified.toISOString();
+    if (this.type.length) map.comment_type = this.type;
+    if (this.permalink) map.permalink = this.permalink.href;
+    if (this.referrer) map.referrer = this.referrer.href;
+    return map;
+  }
+
+  /**
+   * Returns a string representation of this object.
+   * @return {string} The string representation of this object.
+   */
+  toString() {
+    return `${this.constructor.name} ${JSON.stringify(this)}`;
+  }
+};
diff --git a/lib/comment_type.js b/lib/comment_type.js
new file mode 100644
index 00000000..275e4c07
--- /dev/null
+++ b/lib/comment_type.js
@@ -0,0 +1,15 @@
+'use strict';
+
+/**
+ * Specifies the type of a comment.
+ * @type {object}
+ *
+ * @property {string} COMMENT A standard comment.
+ * @property {string} PINGBACK A [pingback](https://en.wikipedia.org/wiki/Pingback) comment.
+ * @property {string} TRACKBACK A [trackback](https://en.wikipedia.org/wiki/Trackback) comment.
+ */
+exports.CommentType = Object.freeze({
+  COMMENT: 'comment',
+  PINGBACK: 'pingback',
+  TRACKBACK: 'trackback'
+});
diff --git a/lib/index.js b/lib/index.js
new file mode 100644
index 00000000..e67817f3
--- /dev/null
+++ b/lib/index.js
@@ -0,0 +1,15 @@
+'use strict';
+
+const {Author} = require('./author');
+const {Blog} = require('./blog');
+const {Client} = require('./client');
+const {Comment} = require('./comment');
+const {CommentType} = require('./comment_type');
+
+module.exports = {
+  Author,
+  Blog,
+  Client,
+  Comment,
+  CommentType
+};
diff --git a/package.json b/package.json
index 9c12cd40..fcbbc589 100644
--- a/package.json
+++ b/package.json
@@ -5,10 +5,9 @@
   "homepage": "https://github.com/cedx/akismet.js",
   "license": "Apache-2.0",
   "main": "./lib/index",
-  "module": "./src/index",
   "name": "@cedx/akismet",
   "repository": "cedx/akismet.js",
-  "version": "9.0.0",
+  "version": "9.1.0",
   "dependencies": {
     "rxjs": "^5.4.2",
     "superagent": "^3.5.2"
@@ -16,14 +15,12 @@
   "devDependencies": {
     "@cedx/coveralls": "^2.0.0",
     "@cedx/gulp-david": "^8.0.0",
-    "babel-preset-env": "^1.6.0",
-    "babel-register": "^6.24.1",
     "chai": "^4.1.0",
     "del": "^3.0.0",
     "esdoc": "^0.5.2",
+    "esdoc-node": "^1.0.2",
     "estraverse": "^4.2.0",
     "gulp": "^3.9.1",
-    "gulp-babel": "^6.1.2",
     "gulp-eslint": "^4.0.0",
     "mocha": "^3.4.2",
     "nsp": "^2.6.3",
@@ -42,7 +39,6 @@
   ],
   "scripts": {
     "coverage": "coveralls --file=var/lcov.info",
-    "prepare": "gulp build",
-    "test": "nyc --report-dir=var --reporter=lcovonly mocha --compilers=js:babel-register --recursive"
+    "test": "nyc --report-dir=var --reporter=lcovonly mocha --recursive"
   }
 }
diff --git a/test/author_test.js b/test/author_test.js
index b80d0c23..07f19aaf 100644
--- a/test/author_test.js
+++ b/test/author_test.js
@@ -1,9 +1,8 @@
 'use strict';
 
-import {expect} from 'chai';
-import {describe, it} from 'mocha';
-import {URL} from 'url';
-import {Author} from '../src/index';
+const {expect} = require('chai');
+const {URL} = require('url');
+const {Author} = require('../lib');
 
 /**
  * @test {Author}
diff --git a/test/blog_test.js b/test/blog_test.js
index 5e578a62..54a13e74 100644
--- a/test/blog_test.js
+++ b/test/blog_test.js
@@ -1,9 +1,8 @@
 'use strict';
 
-import {expect} from 'chai';
-import {describe, it} from 'mocha';
-import {URL} from 'url';
-import {Blog} from '../src/index';
+const {expect} = require('chai');
+const {URL} = require('url');
+const {Blog} = require('../lib');
 
 /**
  * @test {Blog}
diff --git a/test/client_test.js b/test/client_test.js
index 4c50ef99..7ad78d7b 100644
--- a/test/client_test.js
+++ b/test/client_test.js
@@ -1,10 +1,9 @@
 'use strict';
 
-import {expect} from 'chai';
-import {describe, it} from 'mocha';
-import {Observable, Subject} from 'rxjs';
-import {URL} from 'url';
-import {Author, Client, Comment, CommentType} from '../src/index';
+const {expect} = require('chai');
+const {Observable, Subject} = require('rxjs');
+const {URL} = require('url');
+const {Author, Client, Comment, CommentType} = require('../lib');
 
 /**
  * @test {Client}
diff --git a/test/comment_test.js b/test/comment_test.js
index f59ef2e0..2b773afd 100644
--- a/test/comment_test.js
+++ b/test/comment_test.js
@@ -1,9 +1,8 @@
 'use strict';
 
-import {expect} from 'chai';
-import {describe, it} from 'mocha';
-import {URL} from 'url';
-import {Author, Comment, CommentType} from '../src/index';
+const {expect} = require('chai');
+const {URL} = require('url');
+const {Author, Comment, CommentType} = require('../lib');
 
 /**
  * @test {Comment}