TL;DR: The Hosted Apps service has been given a few more months to live. See the Hosted Apps Retirement status page for ongoing status updates.
Several months ago we announced that the Hosted Apps service would be retired.
Hosted Apps was a service that we offered, where various third-party apps (WordPress, phpBB, MediaWiki, and so on) could be used in conjunction with the standard tools offered by the core SourceForge platform.
We’re currently sorting through a scale-up of capacity for the project web and project DB services, and increasing scaling in our LDAP directory infrastructure. As this work, and testing of the platform with modern app revisions, is not complete, we are postponing the end of life of the Hosted Apps offering.
We will continue to update the Hosted Apps Retirement status page as we have more information, and ample notice will be provided when the new end of life date for the Hosted Apps service is announced.