The GPL error with NVIDIA drivers and kernel 4.1-rc has been fixed with a patch to linux/arch/x86/kernel/process.c

Details are at http://lkml.iu.edu/hypermail/linux/kernel/1505.0/03818.html.    EXPORT_PER_CPU_SYMBOL_GPL(cpu_tss); has been replaced by EXPORT_PER_CPU_SYMBOL(cpu_tss);

I have applied the patch to Kernel 4.1-rc2, and rebooted, and NVIDIA driver 346.59 now compiles and loads OK..

Robert Gadsdon.   May 6, 2015.