Shotcut received its first submission for translation to the Czech language. So, I have added support to the code and build system to support the inclusion of languages as of version 12.10.20. This has been integrated and tested on Windows and Linux. I think there is still something I need to do for OS X with plists in the app bundle to support this.
If you want to translate Shotcut first please understand that Shotcut is young and under heavy development, and you should expect many changes over the next few years. Also, the project releases a new version almost daily, and there will not be periodic calls for translation updates; you would be responsible for periodic updates. With that said, please comment here or in the discussion forum if you want to make a translation.
Update: I have since setup a Transifex project to make it easier for people to make and submit translations.