Isn't it incompatible if, and only if, you modify the original? For example, I can make an open source program that uses OpenSubDiv and distribute that open source but I cannot modify OpenSubDiv and distribute the source?
Reading the license text, I do not see any exception for distribution of exact copies. What the license text say's is: if you distribute any portion of the software in source code form, you may do so only under Ms-PL.
Project will use the technology described in the now open patents, but the source code will likely never see any use beyond as a reference manual.
