I first forked language-java (https://github.com/vincenthz/language-java) without the intention of publishing it, i just wanted to add a few features and if it's useful create t pull request to the original project. Here is my fork: https://github.com/exemplator/java-parser
But then things got out of hand, i discovered significant bugs and realised that the features require a complete rework of fundamental parts of the library. I have since touched nearly every line of the project and completely broke backwards-compatibility. Since i think the bug-fixes and features introduced would benefit a wider audience, should i publish my project? This might be a personal thing, but i have to confess that i don't like trying to merge huge amounts of work upstream into private repositories. I like programming and a lot of thought went into my changes, so i want at least some recognition for it (even if nobody ever notices it). Also, the original project is pretty much unmaintained and the work feels wasted if it just disappears into an unmaintained project. So, what should i do?
But as you said, the project is unmaintained and you likely won't get a response. If you don't get a response, then the world can benefit from your fixes.