Well, Piranha Bytes are the developers of Gothic since day 1, JoWood was the publisher at least here in Europe. Lately they had some disagreements about how to go on etc and canceled their relations. Now JoWood owns the rights to the Gothic series apparently, so they will make Gothic 4(and apparently they want to make it more mainstream). Piranha Bytes can make a new game but they can't call it Gothic anymore. I think it's similar to the Operation Flashpoint story where Codemasters will bring OFP2 while Armed Assault is the new game from Bohemia Interactive, the developer.

But the problem with Gothic 3 is that the game was quite buggy and there was (at least they said there was) a patch in the works which was meant to redo a lot of things, fix some bugs etc, they even spoke about redoing the combat system. But since the two companies split up, there will be no more official patch and some community members went and tried to fix what they could fix themselves. Then JoWood went and contacted some of them about forming an unofficial team under the lead of the JoWood community manager. They also wanted to provide the team with some tools and source code and probably money to fix bugs. The result of this seem to be these community patches.

And they're rather small I think, few MBs only.