mathematics itself can't be patented, sure. but it seems their specific application can be -- see: https://datatracker.ietf.org/meeting/92/materials/slides-92-...

galois fields are very interesting for random linear network coding, so of course there is a very thorough patent group (recently sold off, I believe) around it.

given the seriously transformative effects it can have on communications networks -- especially wireless -- I'm both saddened and unsurprised it's in basically nothing as of yet. because it's patented to Hell & Back.