[davikr]

On Windows, try Altap Salamander. It's free and open-source.

[HackerThemAll]

There's the free & open source clone of Total Commander - Double Commander. It's compatible with TC extensions, and just like TC also written in FreePascal.

[gattr]

And Unreal Commander (freeware), also compatible with TC plugins. I'm usually on Fedora, I use Krusader there.

[lysp]

Another option for windows is ZTreeWin (a clone of the old XTree Gold).

Fully keyboard based, and has a shortcut (F8) that goes into split screen mode if you need.

[pangey]

When I was on Windows, I paid for Total Commander. BTW, Altap Salamander is freeware, not open source. It is a decent alternative nonetheless.

[davikr]

It's licensed GPL-2 and on GitHub now.

https://github.com/OpenSalamander/salamander

[ihateolives]

Does it support unicode in filenames yet? I ditched it for FreeCommander for that reason.