>>1526
If your replacement is designed using knowledge you gained from reading the code, then no, your code is now also tainted by their copyright.
Does this make a lot of sense? Not really. But consider that copyright laws were written for mass media, not software, and IBM was happy to abuse a liberal interpretation of said laws to justify control over an entire ecosystem.
That's why clean room design exists. What you
can do is decompile it, pick it apart, write a spec of what should be available, and then hand that to someone else who independently writes code to match a spec. The spec isn't copyrighted and can't be (unless Google loses their battle with Oracle), just the code, but you taint yourself by viewing it. But there's nothing stopping you from giving someone an API to develop.