>>Actually, registration and access to the CS forums is free.
>
>So what could the reason be then? There as to be a logical explanation to this difference in behaviour.

No offense to Tamar < bg >, but CS is older and more "mature" than UT. I think the UT attracted the newer developers when it came on-line 10 years ago. Those that were already using CS, tended to stay there although many cross-over to the UT as well.