add an item about open source

R=rsc
CC=go-dev
http://go/go-review/1025013

doc/root.html

@@ -92,6 +92,12 @@ It feels like a dynamic language but has the speed and safety of a static langua
 It's a joy to use.
 </p>
 
+<h3>&hellip; open source</h3>
+
+<p>
+Go for it.
+</p>
+
 </p>
 
 </div>