Changed license to OpenFlow license.

LICENSE

-Mininet alpha release license
+Mininet Pre-Beta License
 
-(c) 2009-2010 Bob Lantz and Brandon Heller
+Copyright (c) 2009-2010 Bob Lantz and Brandon Heller
 
-Mininet is currently in *limited alpha release*. We encourage you to
-experiment with it and hope that you will provide us with feedback on
-features, documentation, and how you're using it. We plan to make it
-available publicly via a GPL or BSD license (probably in April), but please
-don't distribute the code or URLs yet! The feedback you provide will help
-us improve Mininet for general release.
+We are making Mininet available for public use and benefit with the
+expectation that others will use, modify and enhance the Software and
+contribute those enhancements back to the community. However, since we
+would like to make the Software available for broadest use, with as few
+restrictions as possible permission is hereby granted, free of charge, to
+any person obtaining a copy of this Software to deal in the Software
+under the copyrights without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+The name and trademarks of copyright holder(s) may NOT be used in
+advertising or publicity pertaining to the Software or any derivatives
+without specific, written prior permission.