add LICENSE file

Author: nillerusr

LICENSE

@@ -0,0 +1,43 @@
+               SOURCE 1 SDK LICENSE
+
+Source SDK Copyright(c) Valve Corp.  
+
+THIS DOCUMENT DESCRIBES A CONTRACT BETWEEN YOU AND VALVE 
+CORPORATION ("Valve").  PLEASE READ IT BEFORE DOWNLOADING OR USING 
+THE SOURCE ENGINE SDK ("SDK"). BY DOWNLOADING AND/OR USING THE 
+SOURCE ENGINE SDK YOU ACCEPT THIS LICENSE. IF YOU DO NOT AGREE TO 
+THE TERMS OF THIS LICENSE PLEASE DON�T DOWNLOAD OR USE THE SDK.  
+
+  You may, free of charge, download and use the SDK to develop a modified Valve game 
+running on the Source engine.  You may distribute your modified Valve game in source and 
+object code form, but only for free. Terms of use for Valve games are found in the Steam 
+Subscriber Agreement located here: http://store.steampowered.com/subscriber_agreement/ 
+
+  You may copy, modify, and distribute the SDK and any modifications you make to the 
+SDK in source and object code form, but only for free.  Any distribution of this SDK must 
+include this LICENSE file and thirdpartylegalnotices.txt.  
+ 
+  Any distribution of the SDK or a substantial portion of the SDK must include the above 
+copyright notice and the following: 
+
+    DISCLAIMER OF WARRANTIES.  THE SOURCE SDK AND ANY 
+    OTHER MATERIAL DOWNLOADED BY LICENSEE IS PROVIDED 
+    "AS IS".  VALVE AND ITS SUPPLIERS DISCLAIM ALL 
+    WARRANTIES WITH RESPECT TO THE SDK, EITHER EXPRESS 
+    OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, IMPLIED 
+    WARRANTIES OF MERCHANTABILITY, NON-INFRINGEMENT, 
+    TITLE AND FITNESS FOR A PARTICULAR PURPOSE.  
+
+    LIMITATION OF LIABILITY.  IN NO EVENT SHALL VALVE OR 
+    ITS SUPPLIERS BE LIABLE FOR ANY SPECIAL, INCIDENTAL, 
+    INDIRECT, OR CONSEQUENTIAL DAMAGES WHATSOEVER 
+    (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF 
+    BUSINESS PROFITS, BUSINESS INTERRUPTION, LOSS OF 
+    BUSINESS INFORMATION, OR ANY OTHER PECUNIARY LOSS) 
+    ARISING OUT OF THE USE OF OR INABILITY TO USE THE 
+    ENGINE AND/OR THE SDK, EVEN IF VALVE HAS BEEN 
+    ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.  
+ 
+       
+If you would like to use the SDK for a commercial purpose, please contact Valve at 
+[email protected].