We intend to include as many translations as we can in the next major version of SourceTree for Windows, which is due very soon. We only want to include translations that are complete, or mostly complete, and at the time of writing that only applies to Japanese and Chinese. We have a number of other languages which are around 60% complete but that's not really enough to deploy, we'd like to get to at least 80% before including them. So if you'd like your language to be included in the next update, please help us complete the translation so it can be supported!