I know it can be confusing because of the name, but these are actually two different things:
Dot org is the open source CMS project owned by the WordPress Foundation.
Dot com is a paid website building service owned by Automattic Ltd.
So for ToS;DR purposes they’re different entities.
Can they be unmerged again? Thanks in advance!
I work at Automattic so happy to reply any questions!
Here are some relevant links: