> For a lot of floss software, there isn't even enough documentation in English and looking at communities that tend to have resources in their own languages ...

I agree; many projects (both FOSS and non-FOSS) lack sufficient documentation. However, this is the case whether or not it is English; it is another issue.

More simplified English might be a good idea. There is what is called Simplified Technical English, but that seems to be for aerospace, and perhaps it could be adapted for computer documentation, too.

I am willing to accept contributions of documentation in any language whether English or otherwise for my projects, although I am only writing in English myself, others can write in other languages if they want to do. (However, I generally have no intention to support commands and status messages etc in languages other than English, nor in character encodings other than ASCII.)

For names of stuff (and comments) in the source code of the program itself, I do not consider it too important to write in other languages, although people can try to do that if they want to do. At least for my own projects though, I intend to limit the source code to ASCII.