Comment by nordsieck
7 years ago
>> From what I understand a lot of the kernel work was done by clean-room reverse engineering. One person decompiles and documents the system and another re-implements given the documentation.
> Is that really clean-room, though?
That is precisely the technique that Compaq used to reverse engineer the IBM PC BIOS. I'm sure it can be done in a legally risky way, but the fundamental technique has been quite well tested, legally speaking.
I don’t remember the details of the BIOS case. A BIOS responds kind of like hardware. You put values in a register, trigger an interrupt, and look at the result in another register. As I recall, the clean room implementation replicated the same behavior, which is permitted. But documenting the actual structure of the code, including variable names, and copying that is not clean room reverse engineering from the point of view of copyright law.