7-Zip is a file archiver with a high compression ratio.
This repository is a replica of source code that can be obtained from http://www.7-zip.org/
7-Zip is open source software. Most of the source code is under the GNU LGPL license. The unRAR code is under a mixed license: GNU LGPL + unRAR restrictions. Check license information here: 7-Zip license.
It is quite likely that this repository is out of date so I encourage you to download the source code from http://www.7-zip.org/ directly.