Free Commercial Open Source C# ASP.NET Forum Software - YetAnotherForum.NET
YetAnotherForum.NET (YAF.NET) for ASP.NET is the most established Free Open Source (with commercial options) Forum/Message Board software the web.
Unlimited forums, sub-forums, messages, chat, albums, avatars, private messages, 22 language localization are just a few features. Source code is written in C# and is freely available.
Put community first, join the open internet.