I meant the binary.

With enough patience and spit it should be possible to understand it. And AI can do it while we sleep.

they don't have to give explicit permission though, they just have to not disallow it (which an EULA could do, in the US at least)

De-compilation isn't enough to avoid copyright infringement issues, and if there are patents involved, they can also be an issue.

You're always going to basically be stuck asking for permission, which is the essential intent of intellectual property law.

Which part of looking at the binary to understand how the device works and then writing a driver from scratch that talks to the device would violate copyright?

One would not have copy the implementation. Just use the binary to understand how the hardware device works. Like "Aha, it sends point data as x/y/pressure triplets, each being 16 bit values" etc.

Presumably GP means from the binary form