I think they made a commented disassembly available officially, and there were definitely aftermarket books with blow-by-blow analysis. You could argue it was

I think they made a commented disassembly available officially, and there were definitely aftermarket books with blow-by-blow analysis. You could argue it was imperfect (not exposing every feature it could, and having performance costs, sent a lot of software to bypass it and pound hardware registers directly, creating that weird world of early clones that would run MS-DOS but not 1-2-3 or Flight Simulator) but it doesn't seem like a hostile gesture to external developers. Now it was definitely a legal hurdle if you wanted to make an outright clone, but by 1984 or so, Compaq and Phoenix had solved that problem.