ReactOS was started somehow in 1996 (and still in alpha?), Haiku-OS is in beta 5 (initial release was in 2002 per Wikipedia) and Microsoft required years for creating Chicago/Windows 95 or Longhorn/Vista

How many years do you need to create own OS? Is it even possible?

Przyznam się, że ręce mi opadają, jak widzę idiotyzmy tu i tam. Ale zacznijmy od początku...