Suppose I have a video game, and the player can interact with a computer in the game to find a file. Suppose the player can view the contents of a file in the video game, but otherwise the computer is non-interactive. I.e., the player can browse directories and choose/view a file, but otherwise no programs will be "run" on the computer, nothing will be compiled in any sense, etc. This would, more or less, be no different than browsing source online -- you don't "do" anything with the source code in your browser except view it, you would have to download/copy it to use it in a program.
The GPL says
To “convey” a work means any kind of propagation that enables other parties to make or receive copies. Mere interaction with a user through a computer network, with no transfer of a copy, is not conveying.
In the above example the entire video game would be "conveyed" to the end user, but the game does not entirely enable "other parties to make or receive copies" of the GPL source code in the sense that you can't "transfer" the source code out of the video game to your computer (but you could copy it by hand if you wanted to...).
The video game engine would not be GPL.
Can I include (in the above sense) files licensed under GPL (3 if I have to pick a version), without changing the license of the overall video game? Or would it be safer to use MIT etc licensed files only?