You can do this right now. For example, I have bought retro games from gog and humble that included multiple builds for different systems and platforms, and no restrictions on where you run them - just that you don't distribute them.
You missed the 'arbitrary platform' part of 5he original comment.
We all know steam exists that wasnt what OP meant.
If arbitrary platform X is one that sells DRM free games, then the comment holds true.