Are attempts at custom mission making with the demo assets meaningless ?

[graykin]

If you get it directly from Frictional's store, you get an actual installer that you can love, honor, and cherish...or burn it on a CD or whatever. It does not manacle your soul to any "convenient", authoritative computer program, like Steam does.

As for other locations, like Gamersgate or Direct2Drive, I have no experience with them.