This is a cool historical artifact, and I'm glad MS released it.
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.
but, but -- you're assuming that what I want to do is build on DOS to do what DOS did but better. What if I wanted to visualize the code in some interesting way? What if I wanted to compare the first versions of Linux and DOS and compare them for their modularity and do a research project on how they affected productivity in firms? And these are only the use cases that I could think of while finishing my cup of tea ...
Fair enough, those sound like awesome projects.
The difference between the MS license and most OSS licenses is that this does not include redistribution.
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.
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.