I don't really like the idea of all this red-tape, requiring one license or another. So I have some concerns. Is there a plan to enforce this? If the PKGBUILD is trivial can you reasonably defend a license?

I don't think any of us expect there to be any real arguments from it. There's not going to be much "defending" going on, the only likely situation I can see is if somebody's package gets moved to [community] and they're annoyed that somebody else is maintaining it now. GPL would help clear that up. Another thing is that some people upload copyrighted binaries by mistake. Reminding the maintainer that the entire git/tar ball has to be under GPL would probably help them avoid making that mistake. Having the PKGBUILDs under GPL makes one less thing to worry about when migrating it over towards [community]. Right now in theory you have to make sure both the project /and/ PKGBUILD's license allows you to package it. By asking all PKGBUILDs to become GPL, now all any future maintainers have to do is look at the source.

If I write a patch/etc is it under GPL or is it under the project's original license?

Get rid of the TOS. I don't think the TUs want to become the license

I would say everything being tracked by the Git repo is GPL. So if it's an external patch hosted outside of Arch, then no. Same concept with packages like Dropbox that can't be repacked, so they list the source. This seems fair, if you want free hosting on Arch, you play by Arch's rules. police. I don't think any of us were asking the TUs to police anything. No one was suggesting having the TUs read through all 50,000 PKGBUILDs to check for GPL violations.