I was under the impression their tool translated a .gmk file in to a .ios file which a freely available iOS runner could then consume. I thought that meant essentially translating a document in to a new format, which an iOS runner can then execute.
I guess I'm not clear on the process, though. Is it up to the end user to get the iOS runner? Where does it come from? The decompiler guys said they didn't redistribute it. Is it the end user who downloads some other iOS game then swaps the .ios game data for another? Or is there just a raw iOS runner freely available?
Whether or not you're allowed to publish the resulting game is beside the point. You're allowed to download uTorrent, but you're not allowed to use it to download copyrighted movies. So I suppose you could translate your game in to Apple-format, but not be allowed to publish it - that does not imply the translator is illegal, because the disallowed action is the publishing step, not the translation step.
Further, if it's the end-user of the translator who downloads the iOS runtime and swaps out the game, that's the responsibility of the end-user. It's just like uTorrent - providing a tool that can be used for illegal purposes does not make the tool itself illegal, only that particular way of using it.
I guess there's also a very big grey area around whether the idea of exchanging a data segment in an executable file counts as decompiling, but again, the translator tool does not have to be the thing that does that.
Maybe I spoke too soon and should have learnt more about it before posting my thoughts, but given there's been a decompiler for the ordinary Game Maker for years, it does seem YoYo could have done something long ago to mitigate this, and they seem to have turned to legal threats rather quickly.