This is a question that I've been trying to figure out for a while already.
I'm working on a php project that I will distribute (or whatever word you want to use) under the terms of the Affero GPLv3.
Now I included a piece of code (PHP Simple HTML DOM Parser) that's not under that license (MIT kind of license, apparently) and I started wondering how GPL code gets affected by the code I included... I mean, it's already settled matter that you become a GPL sinner (so to speak) not if you choose to use GPL code mixed with other (proprietary, for example) code.... the sin happens at the moment of redistributing (or propagating or reciprocating or whatever it's called now) the binaries resulting from linking GPL code with code licensed/released under other terms.
But how is it handled when there's no linking? At least no linking to redistribute... think of projects made in PHP or Python, where no binaries are released.