Which is why, in the case of the school and the WebCT deal, you should get thing stratified with a license agreeable to *all* parties before accepting an offer to aid another party in programming something.
Otherwise, if you’re simply working on their product for free.. well.. unless you’ve reserved some right or have some under the law to protest their insisting on fees for their work, you really don’t have cause to complain. Was the person complaining just not used to how the whole “pay for software” world works?
Moodle’s GPL.. that’s like comparing Apples and Orangutans if WebCT is a non-GPL (or BSD style) licensed software. However, if he’s expecting free support.. well.. people need to eat *shrug*.