NMAP still has a semi-open-source license. Not sure if anyone else considers in FOSS, but it’s a critical tool in network security.

Also, I’ve never used any commercial video editing software but kdenlive is awesome.

It essentially splits the archive into multiple rar sub-files (*.r00, *.r01, etc.) and then creates several more chunks that contain parity information (par2 files) that go with it. By doing so, if you then lose *.r45 but get *.r00-r99 you can recover the *.r45 file from the parity (par2) data. It’s pretty slick.