"lossy compression"
Yes, just like human memory.
If I read a bunch of books from a series and extrapolate based on them to form something similar, it's not plagiarism.
If I read your book, then write a book using a similar voice, style, and plot, and do it in a different language - it's not plagiarism if I offer citation. Likewise, if I do so with a verbatim copy in another language. It's an independent effort.
Ultimately, it boils down to what you can get away with. Considering how trivial it is now to re-implement things, I'd say the chance of license enforcement is close to zero for anything open source except in extremely rare situations where there's a lot of money involved.