Violate the GPL - can I say it is mine?

Hi everybody,

I stumbled over this
the subsequent community of

As far I know snippr was an Elgg based community platform. And now a friend has sent me in which the developer talks about a custom-built community application. Is the new site not Elgg based anymore?

But at all this is not really the question. I just want to be sure. Can I use Elgg and say it is mine without telling it is Elgg and/or it is published under GPL2? Can I customize it and can keep it closed source?