https://shatteredreality.itch.io/lemmasoft-assets

This is an example of a project that requires multiple licenses.

In general I agree. But I would like to know how you propose to distinguish what file what license(s) has? Inner "Licenses.txt" file that describes each file?

You can upload more than one file to itch.io. We could just list all the files on the page and have the user select the license for it.