Millennium OS has been in development since April 7, 2004. It was originally created in 1998/1999 by Jonathan Thorpe, who then stopped working on it in 2000/2001, when he found less interest with it. I have asked him several questions, and I've received answers, so here they are:

How long have you worked on Millennium OS?
I have been working on M-OS since I started learning QBasic.

Did you write it alone, or with someone else?
I wrote most of the code alone, but I also worked with Matt Lee and a couple other guys, who helped make M-OS public. My other GUI, QBF OS, was coded with Yousuf Philips (I no longer have contact with him).

Is M-OS free or commercial?
M-OS is free. It has been one of my experimental projects when I was learning QBasic. I don't intend to sell it. I would like to make it available for everyone to enjoy.

Why was M-OS abandoned?
M-OS was abandoned due to lack of time.

Was there ever a website for M-OS?
There was a website at one time. It was: www.millenniumsystems.8m.com. But it looks like it has been taken down.

What do you do now?
I now program most of my software in C in Linux, but have little time for my own personal projects and have to focus most of my time on Uni.