I'm working on a new version that integrates Getting Things Done principles. "Items" will be able to be Projects and Next Actions if you want. You'll still be able to invoice for any Item. There are a bunch of other changes throughout as well. If you're using an older version you'll need to run an update agent (for example, I "Schedule" items are now "Calendar" items.)
As for other languages, I have not had any other requests but if anyone wants to translate it feel free.