Microsoft has officially released the source code for 6502 BASIC under an open-source license, following years of unofficial copies circulating online. Initially developed in 1976 by Microsoft cofounder Bill Gates and early employee Ric Weiland, 6502 BASIC was designed to run on the 6502 CPU, which powered several early personal computers, including the Apple II, Atari 2600, Nintendo Entertainment System, and Commodore 8-bit series.
The software played a significant role in standardizing programming language implementations and allowed early developers to engage in programming with simple commands. In 1977, Commodore licensed 6502 BASIC for a flat fee of $25,000, integrating it into the Commodore PET computers and later models like the VIC-20 and Commodore 64.
Despite the passage of nearly 50 years, interest in 6502 BASIC and the MOS 6502 CPU remains strong. Preservationists and hobbyists have been actively working on FPGA-based re-creations and emulator projects, with the 6502 BASIC code being featured in various museum archives. Microsoft noted that dedicated preservationists have reconstructed build environments and verified that the historical source can still produce byte-exact ROMs.
The release of this open-source version is seen as a continuation of previous efforts to preserve early computing history, building on prior releases such as GW-BASIC, which also has its roots in early Microsoft software. For those interested in exploring the assembly language source code of Microsoft’s 6502 BASIC, the complete code is now available on GitHub.
Source: https://www.theverge.com/news/771120/microsoft-6502-basic-open-source-release