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.
7-Zip is a file archiver with a high compression ratio. Usually, 7-Zip compresses to 7z format 30-70% better than to zip format. High compression ratio in new 7z format with LZMA compression. Supported formats - Packing / unpacking: 7z, ZIP...