Nvidia isn't 'bad' in any normal sense. They just have
not made source
code available for their drivers available under GPL terms as some small
fraction of users would like to demand.
Please see the COPYING file and the GPL licence. If you are creating a
derivative work of the Linux kernel as a lot of us think the Nvidia
drivers for Linux are then you are required to abide by the licence, in
exactly the same way as you are required to obey other licences.
Alan