Take a look at the InfoPoop license agreement for UBB.
http://www.infopop.com/services_sign-up/services_sign-up-licenseagree.html
The W3T license will probably be similiar.
My thoughts on 'powered by' links are as follows.
I don't like them. I sell ads on my sites. Why should they get a free ad?
On the other hand, I have to have something that tells my visitors what it is, otherwise I get lots of 'what is that' e-mails.
So what I like to do is put a 'credits / about this site' link on all my pages.
I use DreamWeaver and here's why...
My host is pair and here's why...
There I not only explain that its wwwthreads, but I really plug it. The program is great, the community is great, the developer is great and so on.
My license agreement with Rick allows this, my feeling is license agreements bought from InfoPoop will not.
I'm pretty sure I will not be purchasing any upgrades from them. I spend 3 months looking for an upgrade from my current system. I chose wwwhthreads and rejected the InfoPoop nazi's.
..
