The way I unterstand it, at least in European practice, the code itself is copyrighted, as in, the actual text, not the concept behing it. Decompiled source is not the same as original source, it goes through rounds of compiler optimisations and the process of reversing that includes a lot of guesswork. So, in practice, decompiling and working on the decompiled source was at least tolerated, probably because it would have been a grey area at worst.
In terms of whether the ‘clean room’ approach is as critical in Europe or not, I can’t be sure. It might be more permissable for someone to use a decompile as a reference and also directly work on a replacement. However I’m pretty sure starting with a decompile of proprietary software as a direct codebase would run afoul of issues.
Otherwise, imagine you have an HEVC encoded rip of a 4K blu ray. You transcode it to AV1. The bytes are totally different, and even the resultant frames are likely not even pixel for pixel identical. I don’t think copyright law would deem that not a violation, regardless of jurisdiction.
The way I unterstand it, at least in European practice, the code itself is copyrighted, as in, the actual text, not the concept behing it. Decompiled source is not the same as original source, it goes through rounds of compiler optimisations and the process of reversing that includes a lot of guesswork. So, in practice, decompiling and working on the decompiled source was at least tolerated, probably because it would have been a grey area at worst.
That is explicitly prohibited by virtually all proprietary software license agreements.
In terms of whether the ‘clean room’ approach is as critical in Europe or not, I can’t be sure. It might be more permissable for someone to use a decompile as a reference and also directly work on a replacement. However I’m pretty sure starting with a decompile of proprietary software as a direct codebase would run afoul of issues.
Otherwise, imagine you have an HEVC encoded rip of a 4K blu ray. You transcode it to AV1. The bytes are totally different, and even the resultant frames are likely not even pixel for pixel identical. I don’t think copyright law would deem that not a violation, regardless of jurisdiction.