AragonX wrote: Well, INAL, but you can't copywright modifications made to GPLed software.
Of course you can. Copyright is what underpins the GPL. The Linux kernel, for instance, contains code copyrighted by a wide variety of people. The copyright for (most of) the IP filtering code for instance is held by members of the netfilter team, and that's what enables them to go after companies breaching their copyright by including netfilter code in their products without offering to supply the source code.
See: http://gpl-violations.org/about.html#history
You own the copyright to the modifications you make, unless you assign it elsewhere.
Paul.