Stella Alternatives
Stella is described as 'multi-platform Atari 2600 VCS emulator released under the GNU General Public License (GPL). Stella was originally developed for Linux by Bradford W. Mott, and is currently maintained by Stephen Anthony' and is an app in the gaming software category. There are eight alternatives to Stella for a variety of platforms, including Windows, Linux, Mac, Online / Web-based and Android. The best alternative is ProSystem, which is both free and Open Source. Other great apps like Stella are Z26, Javatari, Hataroid and Steem Engine.
The ProSystem Emulator is an Atari 7800 emulator for the PC and Windows OS. The emulator was written in C++ using the Windows API and DirectX. It emulates the Atari 7800 NTSC and PAL TV standards.
Z26 is one of the best emulators for the Atari 2600. The author reports that the graphics part of the emulator is nearing perfection to a point that there's little more to fix.
Javatari is a multiplayer Atari 2600 emulator written in pure Java with no external libs. Just open it! Needs Java 6 or greater and Atari ROMs.
Steem is an open source Atari STE emulator for Windows and Linux. It runs almost every ST program ever made without any problems. Steem is designed to be easy to use and has many unique features.
Discontinued
Last news on the official website dates back to 11th August 2011
jGameBase is a fully-featured retro-gaming emulator frontend and game database utility. It is a sister application to the Windows program GameBase (without "j"), the official frontend for the GB64 Collection.
This is the the Macintosh OSX Port of David Firth's Fantastic Atari 800 Emulator. Ported is the SDL version of the Atrari800 emulator to Mac OSX, and added a full native Cocoa interface, including Preferences, Menus, File Associations, Help and more.
Hatari is an Atari ST/STE/TT/Falcon emulator for GNU/Linux, BSD, Mac OS X, Windows and other systems which are supported by the SDL library.