The simple answer is Yes, because My developerWorks itself is a little bit customized version of Lotus Connections 2.5. Another deployment is in Lotus Greenhouse. But are there any other non-IBM's deployments?
And the answer is Yes!
I just googled for a string "communities/service/html/allcommunities" and here what I found:
http://locopo.net:9080/communities/ (look like 1.0 !!!)
http://connections.vss-inc.com/communities/ (more modern 2.5)
http://connections.logicalive.com/communities/ (also seems to me it's 2.5)
http://www.isign-ihear.org.tw/communities/ (my favorite :)
Sure there must be more.
And last, but not the least, another IBM's community place, I even didn't heard about before!!!
Matching: deployment X