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Stuffit Expander 2011 (15.0.1) expands just about any compression format you can think of, including but not limited to: .sit, .sitx, .zip, .tar, .gz, .rar and many others.
This version of Stuffit Expander works on Mac OS X 10.5.x (Leopard) 32-bits or 64-bits (Intel)
expander_installer_multi_4790.dmg (71.11 MiB / 74.56 MB)
Stuffit Expander 2011 v15.0.1 for OSX 10.5 / DMG image
Architecture: 32-bits & 64-bits (Intel)
Mac OS X 10.5 or later
Emulating this? It should run fine under: QEMU