Before you sign an agreement, read Tim Berry's story:
One of them seemed to give them far broader rights than what we'd agreed. The word "unlimited" was there on the page.
"Don't worry," they said, "that paragraph on page two is just for the disk duplicators, we have to have those rights or they won't manufacture the disks. And you're covered with the paragraph on page three, that limits our rights to exactly what we've agreed."