I think you're underestimating the creativity of patent lawyers a bit.
For instance, just off the top of my head, consider this: "OK, you can distribute the source all you want, but as soon as you compile it, you've created a patented product, the binary of which you can't distribute."
After all, the patent itself is supposed to give all the description one needs of how to implement the patented invention, it's when you fix the patent into something real that you violate the patent.
Edit: What drove me to mentioning the separateness of patents and copyright was some of the discussion around GPLv3, e.g. http://fsfe.org/campaigns/gplv3/patents-and-gplv3.en.html#Ex...