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Microsoft Releases 1978 6502 BASIC Source Under MIT License

A permissive release resolves years of uncertainty for preservationists.

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Microsoft 6502 BASIC goes open source
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Overview

  • Microsoft posted the complete Version 1.1 source—6,955 lines of 6502 assembly—to GitHub under the MIT license.
  • Originally adapted for the 6502 by Bill Gates and Ric Weiland in 1976, the Version 1.1 code incorporates 1978 garbage-collector fixes by Gates and Commodore engineer John Feagans and shipped on the PET as BASIC V2.
  • The codebase includes conditional compilation targets for Apple II, Commodore PET, Ohio Scientific systems, the MOS Technology KIM-1, and a PDP-10 simulation.
  • The official open-source release clarifies legal status for previously circulated copies and encourages new emulator, FPGA, and real-hardware projects.
  • Commodore’s 1977 flat $25,000 license put Microsoft BASIC into PET, VIC-20, and Commodore 64 machines, illustrating the model that helped launch Microsoft’s software business.