Microsoft’s 6502 BASIC is now Open Source

[John Kennedy]

"This is BASIC M6502 8K VER 1.1, the 6502 BASIC lineage that powered an era of home computing and formed the foundation of Commodore BASIC in the PET, VIC-20, and the legendary Commodore 64. This very source tree also contains adaptations for the Apple II (“Applesoft BASIC”), built from the same core BASIC source. The original headers still read, “BASIC M6502 8K VER 1.1 BY MICRO-SOFT”—a time capsule from 1978."

https://opensource.microsoft.com/blog/2025/09/03/microsoft-open-source-historic-6502-basic/

[Hans Otten]

The source leaked already several years ago, pagetable has a nice post on that:  Microsoft BASIC for 6502 Original Source Code [1978] – pagetable.com

About the Easter egg: on the KI-1 version answer 'A' to the Memory Size queation and it clears the screen and prints 'WRITTEN BY WEILAND AND GATES'

[Eduardo Casino]

On Friday, September 5, 2025 at 12:58:08 PM UTC+2 h.o...@hansotten.com wrote:

The source leaked already several years ago, pagetable has a nice post on that:  Microsoft BASIC for 6502 Original Source Code [1978] – pagetable.com

Sure, but the real news here is that it's now officially open source! Not that Microsoft was actively enforcing its rights or taking things down, but this move clears any remaining barriers to bundling MS BASIC with CP/M-65 or other projects where licensing was a concern.

[GN Liu]

Starred~