The translations are a mix of auto-translated content (generally of poor quality), and actual translations made by volunteers who've helped out over the years. Go humans!
New translations are always greatly appreciated! If you benefit from the Form Tools project and are bilingual, this is a really great way to give back to the community.
As of 2017, all Form Tools code and translations are now found on github here. To help translate, just click on that link and follow the instructions there.