Satoshi is one of the early users of this forum and contributed more than that for the community to become this big. Don't think of it like he is the one who created the forum. But he created Bitcoin. Threads like these come out when BTC is having a bull run, I don't know why it matters whether this is the domain or not but this is the biggest Bitcoin community. There are a few other threads related to this inquiry like these

https://bitcointalk.org/index.php?topic=2905330.0
https://bitcointalk.org/index.php?topic=2313878.0

How about this? https://web.archive.org/web/20110530213023/http://forum.bitcoin.org
It was hosted before in http://forum.bitcoin.org ?

The original name of the forum is bitcoin forum.

Satoshi last active on December 13, 2010.

Martii Malmi is the original owner of Bitcointalk.org.

Bitcointalk.org started in July 2011.