I don't think you have to be an AHA Member to use this web-site......I am, but I don't think you have to be one.
You don't. The forum is open to everyone. But it serves to bring together the community and the AHA membership as well and that's a good thing.
Open is a good thing in general (source, data, beer recipes...). It might incentivize the AHA membership process if we could have a little badge or something identifying us as AHA members. Or not....whatever, the forum is a good thing.