Currently there is no forums module available for Sitefinity 4.x. We will provide such module in future releases. Please have in mind Sitefinity 4 is a complete rewrite of the CMS and some features available in 3.x are not currently implemented in Sitefinity 4.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items