Calling it a “forum” makes it sound like a phpBB, like intfiction.org, but you mean something quite different. Maybe something more like a Youtube channel?
If you put some videos on a Youtube channel, then called for volunteers to add more videos to the channel, that seems more likely to succeed.
Having said that, I suspect that there are very few people in the world who care to see a Twine tutorial and an Inform tutorial. Maybe better to have a Youtube channel just for videos on a particular platform. In particular, making a video walkthrough of Aaron Reed’s Creating Interactive Fiction with Inform 7 sounds like an interesting and useful project.