I'm aware of a couple RCP applications who have re-implemented Babel-like websites for community translations. However, none of those is likely to be more open and better documented than Eclipse Babel, and none was trivial to implement.
I imagine that at this point, one of the best path for you would be to get familiar with Babel despite the lack of documentation. However, there's https://wiki.eclipse.org/Babel
which already contains a few interesting things to get started. And if some documentation is missing, then "source code is the ultimate documentation" https://projects.eclipse.org/projects/technology.babel/developer