Here is a question that I asked on "AskUbuntu" and I've been suggested to ask it here:
The first one is open source, so anyone could look for backdoors in it -- including you. Of course, it's hard to say if it's actually safe without verifying it for yourself, but it's at least safer than the other two, where the source code is a secret. There's some evidence that other people are reviewing this code, and there's only a couple files, so in practice, I think this code is likely safe, but it really depends on your level of paranoia.
The PPA just has pre-built packages of the first addon. PPA's are not reviewed by Canonical, so you shouldn't assume that they're safe. You should only trust them as much as you trust the author (assuming you have some way of verifying the author is who they claim they are).
In other words: