I have an Android Game I've written that I released under the MIT license. Recently, there have been several people who have downloaded the source of my application, added ads and uploaded it to the Google Play store.
While this irks me, there's nothing legally wrong with what they are doing since my project is licensed under the MIT license. In order to stop this however, I'd like to relicense my application under the GPL.
The entirety of the code in its current state was written by me (minus ~3 lines or so that can be easily removed), however, the app has been translated into a few different languages by users, who have added their translations through GitHub pull requests.
Is relicensing my project under the GPL an good way to stop people from reuploading it as proprietary software with ads?
If I decide to relicense my project under the GPL, do I need to track down everybody who has modified the translation files and get their permission? I know that this is the case when it comes to the code, however I'm not sure how this works with non code assets.