Even without software patents, I doubt it's legal in most of the world to implement something using somebody else's stolen source code. A clean room process would still be necessary.
By country count, in most of the world (>50%), there is not a notion of "stealing source code." There are notions of stealing cattle and pottery. But legal frameworks have not really caught up.
Also, their Clean Room Guidelines: https://wiki.winehq.org/Clean_Room_Guidelines