Re: why on Earth give this away for free to everyone on the planet
Before Microsoft and the ilk, IBM source code was held by nearly everyone, and control blocks of course. IBM part relied on others to fix their code, and often sent smart ones free gifts or bottles.
Pretty sure ICL, Fujitsu, and DEC/PDP gave out source code. Too young to remember CRAY and CDC. Bottom line was that there were no 'memory leaks' and orphaned junk, and one off errors when real SE's could hunt them down.
Then IBM started covering up control blocks and VSAM, and making source code available to SE's where locked up - just in case the OS went into a deadly embrace /loop that could be fixed on the spot - rather than 2-3 days of no ATM's.
Rolling on - the Atari, TRS80, and AppleII had very tight and efficient code, with chess programs under 1K! Now Microsoft is bloatware riddled with poor coding, unchecked parameters, unchecked recursion, and unreviewed code. If it is done inhouse, you have to wonder from the company that retitled machine attendants to 'systems engineers' .