I have a question about special YAF licensing. I've made a ASP.NET software (script), which I want to sell. I also want to integrate YAF forum as a small part of this script.

On the script forum pages I want to keep "Powered by YAF.NET" copyright and backlink, and on the script features page I want to list and highlight that it uses FREEYAF.NET forum (with backlink to this site).

So my question is: should I purchase any license in this case? If so, which one?