Mlem is licensed under Commons Clause.
This means that Mlem is open-source and you can do whatever you want with its source, like modifying it, contributing to it etc., but you can't sell Mlem or modified versions of it.
Coded entirely in Swift to be native to iOS and run on Apple Silicon, there's no plans for Android support, as that would require rewriting the app from scratch in java, which none of us know (nor do any of us know the android app dev process)-- or making a crappy port, which is obviously unacceptable.
As for kbin-- the platform and API are just different enough that they're both incompatible with Lemmy and not very easy to integrate. there's been rumors of kbin development moving towards lemmy compatibility in the future, so we're waiting to see about that. if that happens, and integrating it become easier in the future, we'll see. as of now, however, we have no plans to integrate kbin.