It is 100% free (MPL license) and actively developed. It looks a bit more modern than Far Manager but retains the dual-panel layout.
Since the original won't work, the community has created dozens of "Orthodox File Managers" (OFMs). These replicate the NC interface exactly but run natively as 32-bit or 64-bit Windows applications. Here are the top 3 that you can run portably (no installation, USB-friendly) on Windows 10.
The original Norton Commander is a 16-bit application. Windows 10 (starting with version 7, and completely on 10/11) does not support 16-bit binaries on 64-bit editions. You cannot simply download NC.EXE and run it.
It is open source (since 2016) and actively maintained. It feels like Norton Commander grew up and learned to handle long Unicode paths and NTFS junctions.
If you must have the original NC experience, use DOSBox portable + original NC.exe. But for practical daily use on Windows 10, Far Manager Portable is the best choice.