On the OpenBSD project, a 3rd party port may have almost any license, with all sorts of restrictions. Not a problem. But the licenses in the OS itself are limited, by policy, per
www.openbsd.org/goals.html. X is shipped as part of the OS, so I can understand why a special license might be rejected. Theo determined it was not a Berkeley style license, and, as he mentioned in his announcement, the license made the software "less free." His decision was debated, but it was Theo's decision. His project, his rules.
As for the Linux products/projects, my understanding was the concern that this was special license was incompatible with GPL.