BitTorrent is a proprietary adware BitTorrent client developed by Bram Cohen and Rainberry, Inc. used for uploading and downloading files via the BitTorrent protocol. BitTorrent was the first client written for the protocol. It is often nicknamed Mainline by developers denoting its official origins. Since version 6.0 the BitTorrent client has been a rebranded version of μTorrent. As a result, it is no longer open source. It is currently available for Microsoft Windows, Mac, Linux, iOS and Android. There are currently two versions of the software, "BitTorrent Classic" which inherits the historical version numbering, and "BitTorrent Web", which uses its own version numbering. History Programmer Bram Cohen designed the protocol in April 2001 and released a first implementation of the BitTorrent client on 2 July 2001. It is now maintained by Cohen's company BitTorrent, Inc. Prior to version 6.0, BitTorrent was written in Python, and was free software. Very early versions released prior to December 30, 2001 were released into the public domain without a license. Versions up to and including 3.4.2 were distributed under the MIT license. The source code for versions 4.x and 5.x was released under the BitTorrent Open Source License, a modified version of the Jabber Open Source License. Versions 4.0 and 5.3 were relicensed under the GPL. Version 4.20 of the client was dubbed Allegro by BitTorrent Inc., in reference to protocol extensions developed by the company to accelerate download performance and ISP manageability. Version 5.30 of the client which is snapshotted at Internet Archive is the latest open source version. Since version 6.0, which was released on September 18th 2007, the BitTorrent client has been a rebranded version of μTorrent. It is no longer open source. Features The BitTorrent client enables a user to search for and download torrent files using a built-in search box ("Search for torrents") in the main window, which opens the BitTorrent torrent search engine page with the search results in the user's default web browser. The current client includes a range of features, including multiple parallel downloads. BitTorrent has several statistical, tabular and graphical views that allow a user to see what events are happening in the background. A host of views offer information on the peers and seeds to which the user is connected, including how much data is being downloaded from each and to how much data is being uploaded by each. It has an automatic recovery