license in ReadMe

Author: jan-patrick

README.md

@@ -22,3 +22,9 @@ if Processing prints out another port you have to use this one (instead of 0).</
 <p  align="center">6. Connect the "receive"-Arduino and run the "receive"-Processing sketch and check for the correct port.<br>
 The "receive"-Processing code uses the second possible port, thats why it only works when the other Arduino is connected too - or when you change the port. You can use the list of all available ports Processing prints at launch for that.</p> 
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+<h4 align="center">Attribution Requirements</h4>
+<p align="center">As an open source project, attribution is critical from a legal, practical and motivational perspective. Please give us credits! Common places for attribution are for example: to mention us in your project README, the 'About' section or the footer on a website/in mobile apps. </p>
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+<h4 align="center">License</h4>
+<p align="center">This work is licensed under the GNU General Public License v3.0 license. View LICENSE.txt for details.</p>