What is the alternative to SourceForge?

The alternative to SourceForge depends on which of its jobs you mean: for hosting open-source development, GitHub is the default (GitLab and Codeberg are the strong self-hostable/nonprofit options); for downloading desktop apps, most projects now distribute via GitHub Releases, their own sites, or package managers (winget, Homebrew, Flatpak); and for its software-directory role — browsing and comparing business software — that's the job of dedicated directories like directree, G2 or Capterra rather than a code host.

If you're a project maintainer choosing where to live: GitHub for reach, GitLab for integrated CI and self-hosting, Codeberg for a nonprofit home.

If you're a buyer just trying to find good software: skip the code hosts entirely and use a directory that shows verifiable facts side by side.