MPEG 2 has been patent free since 2018 in US and 2020 worldwide. Along with AAC-LC. They are charging for license key for the usage of that specific decoder block only. i.e The IP of the actual HW decoder, not the codec itself.
MPEG 2 and VC1 is so low in complexity you are software decode it with minimal CPU resource on RPi 4.
The patents were still active, and the technology was still useful, when the Pi Foundation started selling the license keys in 2012. Nowadays... yeah, they're irrelevant.