There are currently some doubts about out-of-tree kernel modules licensed
under GPLv3 and if they are supposed to be able to use symbols exported
using EXPORT_SYMBOL_GPL.
Clarify that "Proprietary" means anything non-GPL2 even though the
license might be an open source license. Also disambiguate "GPL
compatible" to "GPLv2 compatible".
Signed-off-by: Uwe Kleine-König <ukleinek@xxxxxxxxxx>