stalwart-mail-server is not AGPL-3, as built

The Github repository is labeled as AGPL-3.0, but this is not actually the case unfortunately.

At minimum the enterprise crate in the tree is explicitly labeled in the file as non-OSS, and furthermore this create is built as one of the default features, which the PKGBUILD appears to include. Individual pieces of code appear to be if-def'd in other locations as well.

With a quick scan, it appears that building without the enterprise feature would result in an AGPL-3.0 clean binary. However, as the terms of the AGPL-3.0 require providing the source used to build the program under the same license, this approach might still require Arch Linux to delete the code itself from the source tree.

Unfortunately, my reading of the terms of the proprietary license is that any redistribution other than for development and testing of the proprietary source code, or binaries built on that code, is not allowed. That means that it's currently not legally possible to distribute the software with any of the enterprise code. I plan to open an issue about this upstream and request that this aspect of the license be relaxed.

I suggest as an immediate step that we bump pkgrel and build the program without the enterprise crate.