I don't think there's much to gain in releasing it under a broader license - I would imagine that most programs that would need to expand or otherwise build upon this code would be better served by using one of the modern clones, such as http://en.wikipedia.org/wiki/FreeDOS
They have a modern toolchain, are actively in development, and seem like they would be much easier to add features to, if one found themselves with such a need.
I'm a proponent of OSS, and if MS wanted to release this under MIT that'd be great.. But I have a hard time thinking of projects that are stopped by the current license.
My guess is that creating a visualization would be a rather transformative use of the work - Redistributing your resulting visualization would likely be firmly in fair use territory.
Comparing the code for modularity is writing an essay. You don't need a redistribution license for the code to do that.
In any event, I hope they do eventually release using an open license. But as a fan of the history of our industry, I'm glad they released it at all.
You may not distribute or publish the software or Derivative Works.
You may not use or test the software to provide a commercial service unless Microsoft permits you to do so under another agreement.
You may publish and present papers or articles on the results of your research, and while distribution of all or substantial portions of the software is not permitted, you may include in any such publication or presentation an excerpt of up to fifty (50) lines of code for illustration purposes.