We need a lister for SourceForge, in order to be able to archive what's there.
Sourceforge uses the Apache Allura forge under the hood to host open source projects.
Unfortunately, the associated REST API does not offer the possibility to list all hosted projects. A ticket has been created on the subject a couple of years ago but no action have been taken so far.
It is nonetheless possible to do full and incremental listing, using sitemaps and the REST API to query project-by-project information. See a specification blueprint by @zack in T735#51468 below. It has been designed discussing with a SourceForge tech contact.