Looking at the license, it looks like it's possible, but you will need to release your own code under the AGPLv3 license and make it available to others. That means if you add an auth layer on top of the project, you will need to make that layer available under the same license.

> The AGPL License does not permit sublicensing of the code; that is, you cannot rework or add to the code and then close those changes off to the public. The “open source-ness” of the original code follows any update or addition. Both GPL v2 and GPL v3 contain this provision as well.

Yes, but please don't tell no one