You're right that a derivative must be GPL, but wrong if you were asserting that it's not allowed to profit by selling the GPL software.

However, having sold it, you have to provide the buildable source code too, and you can't prevent your customer from giving it all to everyone else if they want to... or even selling it themselves.

Anyways, it would be great if Nokia took GPL and LGPL solutions made by people here, and either packaged them as is or extracted the juicy bits to use in core Maemo apps and system services.

It goes both ways then, because we can extract the juicy bits produced by Nokia in those same apps and services. That's the beauty of the GPL and LGPL - they strongly support juicy bits being taken, improved, and used to make newer better software all round.