Stella is a 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. Since its original release several people have joined the development team to port Stella to other operating systems such as AcornOS, AmigaOS, DOS, FreeBSD, IRIX, Linux, OS/2, MacOS, Unix, and Windows.
Binary DMG for MacOS X (32-bit Universal Binary, version 10.4 and higher)
This is a very old version that supports Mac PowerPC and Intel processors.