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. 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.

WinRAR is a powerful archive manager. It can backup your data and reduce the size of email attachments, decompress RAR, ZIP and other files downloaded from Internet and create new archives in RAR and ZIP file format.

ZArchive is an application to create a single compressed file archive that contains many files. It is compiled using zlibar with FreePascal. Zlibar is distributed with the same modified LGPL as the LCL.