Those are source packages of free/open source software. Files available here generally fall into one of three categories: 1) Orphaned packages (master site is dead). 2) Packages with only one master site. Mirroring them here improves availability. 3) Tarballs rolled by myself (VCS snapshots for -devel ports or when no official source packages are released at all). Feel free to contact me if you have a package to mirror. Note that old tarballs are eventually purged when a new version is available.