That's exactly what I'm getting at, though! Source Filmmaker is like the paper and pencil; it was made to create content. That is its very purpose; it's not anything like, say, taking a screenshot in a Team Fortress match. It renders the image, with lighting and effects just like in any 3D modelling program. It is no different than Photoshop in that aspect, and so it should be held just as accountable if someone misuses it, which is not at all.
Aye, wholly this. In looking at what an artistic tool does you should look at where the artistic merit lies - which, for SFM, is the in quality of the animation.
The models used in the animation are abitrary, and could be anything; the artistic merit would still lie in the lighting decisions, camera angles, skeleton manipulation. Don't be confused between it and screenshots simply because the rendering engine is also a gaming engine.
And given that there's explicit citation that the models are okay to use so long as money isn't made off them, I can't see that being a problem.
However, the artistic merit should still be judged. Just because there's potential in the medium doesn't mean all of its produce should be allowed. Simply posing some stuff and saving the result to produce a rather mediocre, generic and uninteresting image made entirely out of other people's models doesn't show any sort of artistic license...
... but that would lead to case-by-case judgement, and that's why we want to set rules that stop us needing to have to judge every submission individually, right?
There really should be some user-generated content in these sorts of pictures. It shows at least some artistic creativity.