{the entity} of which they are the board does not have shareholders and unless there's something funky in the charter: there's no mechanism to fire members of the board (other than board action). The shareholders of the llc aren't relevant in this context, as they definitely can't fire the nonprofit's board (the whole point of their weird structuring). https://openai.com/our-structure
Pedantic, but: LLCs have "members", not "shareholders". They are similar, but not identical relations (just as LLC members are similar to, but different from, the partners in an partnership.)