I can assure you it was not altruism  ! In fact, it made it darn hard to copy legally (see Eagle Computer) and get away with it. Phoenix had to prove that none of the people who wrote the code EVER read the IBM published code. And I can tell you that nearly all of us in that era had. So while it seems simple, it was a great way to freeze the competition. They had to wait until there were enough assembler programmers on the 808x series who resisted temptation. Copywrite law specifies about 60% commonality I think. So it was harder than it looked.

Eagle did rewrite theirs under duress and while it was a darn good copy the rest of the industy was already moving on to Phoenix. IBM pulled a subtle, well executed strategy. Sadly they blew it in the MCA debacle but hey, all of the companies at that time made a few of those  !

I can assure you it was not altruism! In fact, it made it darn hard to copy legally (see Eagle Computer) and get away with it. Phoenix had to prove that none of the people who wrote the code EVER read the IBM published code. And I can tell you that nearly all of us in that era had. So while it seems simple, it was a great way to freeze the competition. They had to wait until there were enough assembler programmers on the 808x series who resisted temptation. Copyright law specifies about 60% commonality I think. So it was harder than it looked.

Eagle did rewrite theirs under duress, and while it was a darn good copy, the rest of the industry was already moving on to Phoenix. IBM pulled a subtle, well executed strategy. Sadly they blew it in the MCA debacle, but hey, all of the companies at that time made a few of those!