This game entry includes both the First and Second editions of GURPS. They were largely compatible - and hence are being grouped under one game entry. Any individual books that were released in multiple editions will be shown with the edition in parenthesis.
While most people know the name and what it commonly stands for, what they don't realize is that GURPS originally stood for "Great Unnamed Role-Playing System", as Steve and company couldn't decide on a name for it for the longest time. This was occasionally mentioned in the Space Gamer magazine.