I cant speak much on your main issue, but im the maintainer of ogsapi, and you are correct that it requires an account, thanks for mentioning it, i hadnt considered unauthed requests. I can try and see about updating in the next few days to allow for the requests that dont require auth to be called.
However, if you do plan on grabbing all games from OGS, you might want to use the termination api: Can we get an SGF database dump? - #6 by anoek
And maybe let anoek know that youll be hammering the api for all games?