I’m not sure how it would be possible to translate a KeePass plugin (at least one distributed as a plgx like KeePassRPC needs to be). I’m hopeful that there is now a way but it wasn’t possible when I last tried many years ago. Unfortunately I won’t have time to investigate that myself for the foreseeable future.
Sorry for the slow update of the Kee extension, I’m not far off getting the next beta version ready but it will still be some time before I’m able to release that as a new stable version. The next version will contain a variety of changes to the user interface, although I’m trying to reuse existing translated strings where possible.
Given the extra pressure extension reviewers for Firefox and Chrome are under at the moment, I don’t want to be releasing too many different versions in a short space of time but if it looks as though it will be a long time before I can request the release of the new version, I’ll look into asking them to publish a small update focussed on updating any strings that have been translated in the past year.