> Since when could you buy COTS and expect to get the code too?
Since the 1950s and 1960s. IBM, for example, provided source code for their products until 1983.[1] The full Apple II source code was included in the Apple II Reference Manual;[2] similarly for the Atari 400/800 Technical Reference Notes.[3]
1. https://books.google.co.uk/books?id=hSBrPSYgjI4C&redir_esc=y (page 59)
2. https://archive.org/details/applerefjan78/page/n78/mode/2up
3. https://archive.org/details/CO16555AtariHomeComputerTechnica...