Linux

It's not a Linux distro. It is an opensource reimplementation of the NT kernel and Win32 userspace.

I could see it being useful, if you have a Windows application that runs on ReactOS and you want to save licensing costs (especially if you think of large scale deployments) or it doesn't run on newer Windows versions, but you still want a supported operating system. It is also useful, if you rely on Windows drivers for the hardware, as they should work just fine on ReactOS.

You could also use it as a baseline for your own NT OS, e. g. to compete with Microsoft (if you're brave enough ...). Or you could set up container clusters with an NT base, if you develop container tools for it. :D

I actually wanted to use it once for a VM, but my application didn't run on ReactOS.

I think we miss out on the true potential, because development is just way too slow and there is no release cycle, upgrade path or guaranteed updates at the moment.