Can permanently free decals be used in an open source project?

Our project is currently on a private GitHub repo and we are still deciding on our exact license (might be custom). At some point it will be switched to public and have an open source license.

Can decals from a permanently free collection be on such a repo?
If we bake those decals into a larger texture, can they be present on the repo in that form?

I would also like to know how to get an authoritative answer on this.