TV's Frink said:

Put yourself in adywan's shoes. Would you be willing to risk it? I certainly wouldn't.

Having chatted to Ady earlier about it, I now know edits would potentially stand in a more precarious place legally than fanfilms do as they make use of the existing material rather than making their own.

I feel pretty stupid not to have considered that it's not just the issue of intellectual property, but rather the intention to distribute the original material, altered or not (potentially to people who haven't paid for the official releases).

So no, I wouldn't risk it - though when I posted what I did, I'd wrongly deduced that there wasn't any risk with non-profit projects. I just hadn't considered all the facts, that's all, so I retract what I said :)