7-Zip is a file archiver with a high compression ratio. 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. 7-Zip works for Windows 7, Vista, XP, 2008, 2003, 2000, NT, ME, and 98. And there is a port of the command line version to Linux/Unix. Most of the source code is under the GNU LGPL license. The unRAR code is under a mixed license with GNU LGPL + unRAR restrictions. Check the license for details.