Hey, what do you mean by bitcoin is sponsoring the forum?
Your bitcoin does not sponsor the forum if you did not donate bitcoins to this forum for a VIP or donator membership or did not use bitcoin for purchasing a Copper membership.
It's a Bitcoin forum and there were many Bitcoiners who were forum members and donators for VIP / donator badges. Their bitcoins sponsor the forum many years in the past and until now, also move towards future.
List of donators in bitcoins.
https://bitcointalk.org/donate.htmlTake it as the forum url implies bitcointalk.org. Nothing much.
It's the Bitcoin forum, Bitcoin talk forum, the name says it all.