I feel like the best of both worlds would be to open up the Lemmy interaction code, so it can stay in sync (ha!) with the fast moving development of the fediverse (and maybe allow for community-developed kbin support or whatever else down the line), while keeping the UI and whatnot proprietary (as that's the real secret sauce of an app like Sync, and I imagine there would be code shared between Sync for Reddit and Sync for Lemmy)

Of course it's LJ's decision, but this is just my 2 cents.