Those are all disassemblies, not the original code (although the original code for 6809 BASIC was recently found, see https://github.com/davidlinsley/DragonBasic). Similarly, the blog post links a version of 6502 BASIC by Michael Steil on Github that's set up to build the BASIC ROMs for a variety of computers, but that appears to be based on a disassembly rather than the original code as well. Here's a random bit of code (the code handling processing a FOR statement) from Microsoft's repo, vs. the same code from Steil's repo: https://github.com/microsoft/BASIC-M6502/blob/main/m6502.asm... https://github.com/mist64/msbasic/blob/master/flow1.s#L3

I think it was released in scanned form from a printed document (or maybe that was 8080 BASIC), this is the first I've seen in digital text form.

Ok, so the scanned version was indeed 8080 BASIC. However, the 6502 source has been available unofficially since at least 2015. https://www.pagetable.com/?p=774

Nice to see it out there under the MIT license, certainly. This makes it legal to actually use in many scenarios where it wouldn't be legal to use it previously.