They are all clones of the DOS and later Windows software called Norton Commander.
Yes, I even have a copy of the Windows version of the original Norton Commander.
I used version 2.0 of NC in DOS 3 and version 3 in DOS 5.
I still miss the embedded viewing with Ctrl-Q that midnight commander is missing.
And I still prefer NC over TC, because it was so consistent.
yes, there was also "far", loved that one.
I find the newer ones (especially total commander) much better than nc/mc.
Still is, active and opensource:
http://www.farmanager.com/opensource.php?l=en
As for open source - this one is, but it's written in delphi (pascal?) which makes it hard to contribute. Then again, it works well, so not sure what to contribute anyway.