Tested the 4.2 Final kernel, and the later NVIDIA drivers still fail to install, with the same GPL-only error..
A simple patch to fix this was proposed for 4.2-rc5, some time ago, but – for some reason – has failed to make it into the ‘final’ release..’
Details of the patch are here: http://lkml.iu.edu/hypermail/linux/kernel/1508.0/02260.html
Maybe this will be fixed in 4.2.1, but maybe we have to wait for 4.3-rc1?
Robert Gadsdon. August 31, 2015.