In a strange move, Sega has "legitimized" ROMS hacking. Owning any Genesis classics on Steam gives you access to the new features and susbribing to a mod allows you to boot that game with the relevant mod or hack.
If you poke around in the files, you'll find the ROM files of the games you own now. Before they were encrypted.
I was expecting the mod support to be in the form of IPS patches applied at runtime or something like that. Nope, the BIN file is right there, even if you don't own the game it's listed as a mod for. The pirate Rockman X3 port is on there under Golden Axe. I don't own Sonic 1 on Steam but I could download the homebrew Sonic Megamix.
It's neat to see Sega leverage this side of the community to sell their back catalog, but I'd like to see some more original works come from this. Right now it's existing hacks and questionable copyrighted content. I don't think anyone else would do something like this, as cool as it would be to see, Sega is the one who's resold their back catalog too many times already and there's not much left for them to do but this.