PGP is Pretty Good Privacy software (
http://en.wikipedia.org/wiki/Pretty_Good_Privacy )
GPG is GnuPG, Gnu Privacy Guard (
http://en.wikipedia.org/wiki/GNU_Privacy_Guard )
The both software are similar (except PGP is more commercial than GnuPG).
They are usually used to :
- send secret (encrypted) message between 2 persons.
- send a signed message and the reader can check and be sure the message has not been changed.
This last feature can be interesting for lua/love.
This kind of software are massively used on linux distributions. Each software (packages) are signed with the author(s) keys and the distribution team key.
Even Microsoft started to use PGP signature in his security newsletter to allow people to check that the content of the newletter is not changed.
In the case of love ...
Currently you can check the content of a .love file before running it.
But in some case (for example : LUBE) when you run the game, it download some update, and automatically load them.
By this way you can not check if something is bad inside the updated files.
This feature don't protected again bad authors, but it protected you if the remote server (where the game try to download the updates) are hacked.
Another advantage is when every developers sign their files, you can always know who is the autor, where report a bug and must of all, who is the legal owner of the code (who choose the licence).
If you want sell, or distribute freely your game, you normally only able to do that if you know and respect the whole licences of every part of the code. The worst case is having a good game with some part built over unknow part of code.
I'm almost sure I'm the only one game author that is thinking about the licence... but it's not a problem
For my last argument, if nobody is afraid, I can build a virus with love, for demonstration
Best Regards