I have a question about the GPL licenses and I'm kinda confused. What if I, let's say fork elgg, and create a product to offer for anyone, would I have to give the code or something like that?

http://docs.elgg.org/wiki/License

A related point: If i understand https://github.com/Elgg/Elgg/blob/master/_graphics/SPRITES_LICENSE.TXT correctly then probably many pleople are violating this licence. --> IMHO: Goal should be: Make the Elgg licence as simple to understand and use as possible. So no AGPL, no different licences for different parts. As other communities had these discussions as well a look over to Drupal might help. https://drupal.org/licensing/faq