I will make this change after the next Nabble release, which should happen in a week or two. The current release has a problem that prevents me from doing this change easily. So please wait a little bit.
It would be great if you could create a sub-domain for those forums, something like "forums.openbabel.org" and then use our custom domain name feature (it is free, like everything in Nabble). Users will feel more confortable with such URL.
I will let you know when you are the new administrator.
http://open-babel.957263.n4.nabble.com/