This goes for any phone app:
- No onerous Terms of Service Agreement required
- cheap and easy to develop
- Easy to make fully open source apps
- great backwards compatibility (some apps built for Android versions from 13 years ago can still be used)
- no need to be locked into Apple’s ecosystem
- no need to pay Apple fees to “be a developer”.
- easy to load apps into phone without going through the official store or “test flight”
It’s non-free, it’s non-libre, but it does pass the bar of open source software. The OSI, EFF, RMS or whoever don’t have to say it is in order for it to be true.
You can distribute it but there are limitations on it, you can make a fork of Grayjay that is free to use, review, re-distribute and add parts to it adhering to other open source licenses from whence they were developed as long as it’s non-commercial, and doesn’t make any representations on behalf of FUTO or Rossman, essentially.