Nowadays, not much except for legacy embedded use. (Though in practice, the stability of ReactOS isn't great and also there's the untested licensing situation o

Nowadays, not much except for legacy embedded use. (Though in practice, the stability of ReactOS isn't great and also there's the untested licensing situation of ReactOS. Allegedly some of the code might have been lifted from Microsoft code. This issue alone may have made companies stay clear of it.) But way back when, before everything computing metastased into a fluffy Javascript cloud world, and when Linux wasn't as mature, an "Open Source Windows NT 4" would have been a great off-ramp off Microsoft. You know, "Year of Linux on the Desktop" which was such a coveted thing, could have been "Year of Open Source Win32" instead. Instead, the Desktop waned in importance, we got cloud services and smart phones instead, and Linux grew up to be a force in its own right.