This is a very good question indeed. Personally, I happen to be working with the "standard" modules and I rely on the versions being installed by web providers on webservers, so this didn't seem to be an issue. Are there any known problems to the core modules? I guess the only correct and proper way to be really sure is to copy the license text of all modules you are supposed to use, and send it to your company's lawyer or law expert.
In Germany, the law only allows for legally qualified people, like lawyers and judges, to give advice on such issues. As a programmer without official qualifications in law, I have to state that my advice is nothing but my personal point of view. So, it's up to the lawyers again, if there should be any doubt about licensing.
