I think Migaku only uses MoEDict, which we also use? Not every MoE dictionary is under an NC license. We have made inquiries with the MoE about this stuff in the past and they never get back to us.
Oddly enough the "oo inn" app you mention uses their Hokkien dictionary but in its acknowledgements page it claims it's under a BY-ND license while it's currently listed under a BY-NC-ND one; checking other listings for the dictionary its seems like it was formerly under BY-ND but then they added the NC for some reason?
Anyway as I said we will happily post their dictionaries here, probably as an unchanged mirror of their original files, with instructions on how to import them into a Pleco user dictionary, and we can probably also add presets for some of these files to the Pleco user dictionary import screen to make that process easier. And of course if anybody else wants to privately share the resulting user dictionary file, that doesn't create any violation on our end. But I don't currently see a way to streamline this beyond that - we have to be very very scrupulous about dictionary licensing since we offer so many commercial ones.
It's really not hard now, though - if you create a new user dictionary you'll see both Hokkien and Hakka as options for the primary reading language, just do that and then pick a dictionary data file to import and make sure that the fields were detected correctly before you import it.