Yes. The main feature is the slopes and curved platforms (which would be mostly useless in a MMX-style game), there's no system for different weapons, and so on.
It's still breaking both the EULA and intellectual property laws... Yoyo are backed by the guys that owns OpenAI now so you probably don't wanna pick a legal battle with them if you can avoid it.
You might be interested in the open source alternative LateralGM / Enigma though? (I think it's still around). It's basically a recreation of GM8 and Studio 1.x in Java. I remember it was a bit of a mess to set up since it's two separate projects (for the IDE and compiler) and you need to jump through a few hoops to glue them together, but it's less legal risk and probably less virus/spyware risk as well.
If you bought it on Steam you should be able to download the standalone version from your Yoyo account? I have some faint memory every Yoyo license comes with a matching Steam key and vice versa.
(You should probably contact Yoyo's support about this and not me, I don't work for Yoyogames so I don't have the latest information)