reactos

Netstat -vat: "I've been writing about the ReactOS for at least five years (the project itself is more than 10 years old).

It's an effort to try and replicate a Windows operating system in open source."

Wine-Reviews: "There have been several attempts down the years to make Windows unnecessary. The most audacious is doubtless ReactOS, which cuts to the heart of things and wants to be a complete Windows XP-compatible OS."

Information Week: "We look beyond the traditional open source OS of choice to other free options such BSD, OpenSolaris, HaikuOS, ReactOS, and PureDarwin."