Actually, given the content and purpose of the movie, I think using Kazaa, IFilm, your nearest Newsgroup server, or any other means available, whether it leads to "box office" or not, would be appropriate. I don't think Mel did this one for the money. I'm sure he'd like to use normal channels and see it be a success, but the reason wouldn't be the money itself (except to allow him to make another one like it).
Going the normal route and being successful with this film might entice the normal Hollywierd types to try making films with pro Christian themes. Many of them aren't driven by being pro or anti Christian, even though they may use lots of anti-Christian themes. They do what they do because they think it will bring people into the theaters and make money for them.
But that's all minor compared to what telling this story to a new generation and to a very weary and hurting world means. If he has to stand on a street corner giving out DVDs that he payed to get pressed, I think he'll do it. I'd kick in to help pay for that.