Are you using any "open source" program/framework/tool for commercial purpose? You might want to know more about the licensing issue if you are.
HOWTO: Pick an open source license (part 1) by ZDNet's Ed Burnette -- If you write some code keep in mind that it's yours and you get to decide if, how, or under what circumstances, other people can use it. Let's say you've made the decision to release your code as "open source". What does that mean, what is an open source license, and how do you pick the right one? This question comes up all the time so I thought I'd write up a simple decision tree to try to explain the choices.