A lot of the core code (and dissapointingly, btrfs) is GPLv2-only. So rewrites are unlikely, you'd have to ask contributors to update the license. Just do a gr

A lot of the core code (and dissapointingly, btrfs) is GPLv2-only. So rewrites are unlikely, you'd have to ask contributors to update the license. Just do a grep for "at your option", since that's the wording in the copyright header to specify that it's released under GPLv2-or-later, tells me that it isn't that great. It's around 10000 files (Linux has ~50000 files) so it's ~20% of files. This doesn't account for documentation or files that don't specify that they are under GPLv2-or-later.