You sir, are a great astroturfer and deserve a raise from MS.
Well, just recently a very interesting article covering Microsoft "open source .NET" license, you should read up on that, especially MS requiring a license to the patents in the code you contribute, but refusing to grant you license for their code, instead, providing a promise not to sue.
Um... Mono is released under an MIT license, which is less restrictive than the Microsoft Public License. But here, take a look what Microsoft's Open Source license says in terms of them licensing you their patents on their code:
2. Grant of Rights
(A) Copyright Grant- Subject to the terms of this license, including the license conditions and limitations in section 3, each contributor grants you a non-exclusive, worldwide, royalty-free copyright license to reproduce its contribution, prepare derivative works of its contribution, and distribute its contribution or any derivative works that you create.
(B) Patent Grant- Subject to the terms of this license, including the license conditions and limitations in section 3, each contributor grants you a non-exclusive, worldwide, royalty-free license under its licensed patents to make, have made, use, sell, offer for sale, import, and/or otherwise dispose of its contribution in the software or derivative works of the contribution in the software.
I'm not going to reproduce Section 3, but the restrictions are: You don't get a trademark license or a warranty, you're not allowed to sue other licensees over your patents, you have to retain copyright notices that appear in source code, and you can't re-license MSPL code under viral licenses (e.g. the GPL).
If you want to see the full license, check out the OSI's site on the MS-PL