I was initially going to post this on softwareengineering.stackexchange but after some research I believe this might be more on topic here.
I was recently faced with the problem of needing an open source substitute for a closed source commercial software library for a personal project, mostly because the library did not offer bindings for the language I was working with.
While I later abandoned this approach I initially thought it might be a reasonably idea to reimplement the libraries API myself in the target language. But then I remembered that a couply years ago Oracle had successfully sued Google over their commercial use of a reimplementation of one of their APIs (see this post for reference). While I don't believe any of my personal projects will ever have enough impact to incentivize a large corporation to sue me and I'm also not to sure about the actual licencing/copyright of the library in question this made me wonder whether this court result also sets a precendent for cases like mine in which the functionality of some API is replicated in a sufficiently different technology.
I live in Europe but I would be content with an answer based on US-law, this is solely a matter of interest.