7-Zip is a file archiver with a high compression ratio. The download links above redirect you to download pages on SourceForge.net
License
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.

You can use 7-Zip on any computer, including a computer in a commercial organization. You don’t need to register or pay for 7-Zip. But you can make a donation to support further development of 7-Zip.
The main features of 7-Zip

* High compression ratio in new 7z format with LZMA compression
* Supported formats:
* Packing / unpacking: 7z, ZIP, GZIP, BZIP2 and TAR
* Unpacking only: RAR, CAB, ISO, ARJ, LZH, CHM, MSI, WIM, Z, CPIO, RPM, DEB and NSIS
* For ZIP and GZIP formats, 7-Zip provides a compression ratio that is 2-10 % better than the ratio provided by PKZip and WinZip
* Strong AES-256 encryption in 7z and ZIP formats
* Self-extracting capability for 7z format
* Integration with Windows Shell
* Powerful File Manager
* Powerful command line version
* Plugin for FAR Manager
* Localizations for 69 languages

7-Zip

7-Zip works in Windows 98/ME/NT/2000/XP/Vista. There is a port of the command line version to Linux/Unix.