A typical Linux system is largely comprised of unrestricted, open-source software. But some of the most popular software around is either closed-source or open-source, but restricted by patents.
Jun 14 17:38:21 matt-laptop kernel: [70535.183694] WARNING: CPU: 2 PI 0 at /build/linux-lts-vivid-naHA4g/linux-lts-vivid-3.19.0/ubuntu/i915/intel_display.c:11100 ...