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.
: Utilities like The Unarchiver or Keka are common choices. Two-B.7z
7z code is a part of 7-Zip program distributed under the GNU LGPL. You can download 7-Zip sources and binaries from Download Page. You can use 7-Zip on any computer, including