Gamemaker

free? when?

Περίμενε το Halloween Steam Sale τότε. :P

The base software is still free on Steam, but the pro upgrade was on a recent bundle.

99% sure it was never free, the dlc's atleast.
Base game is free, the rest was in a bundle.

It was in a Humble Bundle that just ended.

8 people have it listed for trade on barter.vg
https://barter.vg/i/3335/

There's people beta testing a major update that is expected to be sold as a higher tier product which means the existing version may be bundled again or cost reduced in the future.

You can do most of the stuff with the free version and if you finish your project then get the pro so you can sell it or you could try Unity or Unreal both of which have free versions that collect a % if you have a hit (make over $100K sales or something like that). The new Source engine has been deployed in the new DOTA2 but isn't being offered to the public yet and is expected to have a free + you must sell it on Steam rule.

IMO there's nothing special about Game Maker Studio.. You could look at Godot instead, which is free and open source.