Quote: "Anyway, like I said, until Valve comes a'knocking, I wouldn't worry too much"
No offence to you Jiffy, but that's a horrible piece of advice. Thats akin to saying: "Till you get caught shoplifting, is it really wrong? or: "Till I'm caught, driving under the influence hurts no one."
If you have a question, your best off to ask on the Valve forums. Write the company if you don't get an answer you feel comfortable with.
I know Lucus Arts often highlights and showcases fan based movies and games. Their view on is if you're not making any money off of it knock yourself out. Blizzard on the other hand will send people to your door in suits 4000 miles away handing you a "cease and desist" order (the owners of Blizzhackers comes to mind personally).
Valve may not take this stance, and certainly no one here can answer for those guys. Certainly don't allow anyone around here to be your moral compass, including me. You know what's right, and here isn't the place to find the answers......