Apache 2 is important to avoid things like the situation with LLVM where aggressive patent holders like Apple and Qualcomm feed the project with patent encumbered contributions, so that sorting out what parts of it that you're patent exposed on or not is basically impossible (meaning, you'll take a blanket license at your expense if you depend on it).
If you're not using a more modern license with an explicit patent grant you should at least have some agreement from contributors to make any of their own patents required for their contributions available to all other users of the software and its derivatives. Otherwise you may find that your permissive licensing isn't.
> If you or your employer own the rights to a patent and would like to contribute code to LLVM that relies on it, we require that the copyright owner sign an agreement that allows any other user of LLVM to freely use your patent.
A copyright license that includes an explicit patent license would allow non-LLVM users to use the patents as well, as they would need to be able to in order to exercise their rights under the LLVM copyright license and use LLVM code in something that is not LLVM.
If you're not using a more modern license with an explicit patent grant you should at least have some agreement from contributors to make any of their own patents required for their contributions available to all other users of the software and its derivatives. Otherwise you may find that your permissive licensing isn't.