Microsoft Reciprocal License

This license, much like the Microsoft Public License, is open source and comes with a patent grant. However, it requires that any derived file under the same license be given a source code.

Full License Text

Microsoft Reciprocal License (Ms-RL)

This license governs use of the accompanying software. If you use the
software, you accept this license. If you do not accept the license, do not
use the software.

1.  Definitions
The terms "reproduce," "reproduction," "derivative works," and "distribution"
have the same meaning here as under U.S. copyright law.

A "contribution" is the original software, or any additions or changes to the
software.

A "contributor" is any person that distributes its contribution under this
license.

"Licensed patents" are a contributor's patent claims that read directly on its
contribution.

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.

3.  Conditions and Limitations
     (A) Reciprocal Grants- For any file you distribute that contains code
     from the software (in source code or binary format), you must provide
     recipients the source code to that file along with a copy of this
     license, which license will govern that file. You may license other files
     that are entirely your own work and do not contain code from the software
     under any terms you choose.

     (B) No Trademark License- This license does not grant you rights to use
     any contributors' name, logo, or trademarks.

     (C) If you bring a patent claim against any contributor over patents that
     you claim are infringed by the software, your patent license from such
     contributor to the software ends automatically.

     (D) If you distribute any portion of the software, you must retain all
     copyright, patent, trademark, and attribution notices that are present in
     the software.

     (E) If you distribute any portion of the software in source code form,
     you may do so only under this license by including a complete copy of
     this license with your distribution. If you distribute any portion of the
     software in compiled or object code form, you may only do so under a
     license that complies with this license.

     (F) The software is licensed "as-is." You bear the risk of using it. The
     contributors give no express warranties, guarantees, or conditions. You
     may have additional consumer rights under your local laws which this
     license cannot change. To the extent permitted under your local laws, the
     contributors exclude the implied warranties of merchantability, fitness
     for a particular purpose and non-infringement.