Hi
A forum space is still just a space, so you can use the same URL pattern as for spaces. The tricky bit is finding the space ID, since the links aren't on the forum's details page. We'll look at adding that in.
We don't use the Alfresco forums to power our own forums yet, because we really need to add a few more features to meet people's expectations of a public forum. We will switch to it as soon as possible!
I notice your site has blanked the powered by Alfresco logo - which goes against the licence terms (unless you're a customer or partner). 😉
Regards
Paul.