It’s definitely a Lemmy issue. I’ve been jumping between apps to test them out (wefwef, LiftOff, and Memmy) and they all show the same posts for All/Hot. Active is a bit better, but since it opens the time range to a couple days, a lot of stale posts show up. Hot is just polluted with “spammy” posts by bots, so ended up sticking with Active until the Hot algorithm is sorted out.
So, question of if they’re safe or not will come down to HOW they did the reverse engineering. If the same engineers that delved into the jailbroken iOS devices are the ones that wrote the code (which seems likely given the prototype came from a single person), they’re going to be in trouble. If they implemented a “clean room” reverse engineering though, then they’re likely safe from being sued over copyright violations. See Wiki