Yeah, it’s essentially just allowing people to substitute their own assets and build their own new games using the existing codebase. Like imagine if anyone could just use the StarCraft engine to make new RTS games. It means RTS games would be much easier for casual makers to work on.

It also means modders can directly access the code, to make custom mods that work directly with the game. Historically, unless a game has built-in mod support, modding is just a sort of “bolted on” addition. Because without having the source code, it’s really difficult to know why your mod that changes some seemingly small thing is breaking the entire game. But if you can see why it’s breaking things, you can devise ways to work around it.