If Jahia is open source then maybe Windows is. The license is closer to Microft's shared source concept than anything than meets OSI standards. Whether or not I pay for the code has nothing to do with "open source", it's that I get the source code AND I am free to do what I want with it. It also has nothing to do with collaborative development other than most open souce projects are developed collaboratively. They don't have to and as you have proven you don't have to be open source to develop collaboratively.

At least Caucho (Resin) were polite enough to stop calling themselves "open source" awhile ago.

http://www.opensource.org