codeigniter.com has been around forever, even in the old EllisLab days.
EllisLab registered some additional domains, perhaps even codeigniter.org (I can't say for sure), but found that codeigniter.com was the only one that really mattered.
If codeigniter.org was used, my guess it that it mapped to the same server/instance as codeigniter.com
CodeIgniter is still a community-driven open source project