This is some seriously cool ****. Check it out:
They have just gone Open Source and put the code on GitHub.
It's not as useful for tiny phone screens, where you need every pixel for just a single app. But for tablets -- especially the 7" and 10" sizes -- this is a huge deal. Android tablets can now actually be used for real work.
I would love to see this in CM9. So far, no official APK has been released, and it's not clear whether a deeper level of integration is required from ROM vendors. I've asked some basic questions on their Google group for Cornerstone development:
In order to control the screen display of other 3rd-party apps, Cornerstone does in fact make changes to the Android "/framework" code. (There are those framework changes, plus two APK packages that provide the GUI for launching and managing apps.)
This means that Cornerstone support would need to be integrated into the ROM directly. It cannot simply be installed with an APK. I'm fairly new to Android development, but it seems like it would be necessary to apply their changes to the Cyanogenmod GitHub tree and then build a new ROM for your specific device.
It would be easiest for users if the CM team if they integrated the support directly into their tree; then users would be able to choose to use the end-user APK files or simply not use them.