On the last point, it's interesting to note that, at the time the IBM BIOS was being reverse engineered by various parties (around 1981/82), software patents we

On the last point, it's interesting to note that, at the time the IBM BIOS was being reverse engineered by various parties (around 1981/82), software patents were still not particularly well established. It wasn't until the Federal Circuit was established in '82 that there was a consistent treatment of software patent litigation: https://en.wikipedia.org/wiki/Software_patent#United_States https://en.wikipedia.org/wiki/Software_patent#United_States One has to wonder if, today, the reverse engineering of the IBM BIOS would be possible, given the likelihood that IBM would've patented their implementation.