Update index.html

Author: rocky

index.html

@@ -31,7 +31,7 @@ <h2 id="project_tagline">A free, open-source alternative to Mathematica</h2>
   <!-- MAIN CONTENT -->
     <div id="main_content_wrap" class="outer">
     <section id="main_content" class="inner">
-      <p>Mathics is a free, general-purpose online computer algebra system featuring Mathematica-compatible syntax and functions. It is backed by highly extensible Python code, relying on <a href="http://sympy.org/">SymPy</a> for most mathematical tasks.</p>
+      <p>Mathics is a free, open-source general-purpose online computer algebra system featuring Mathematica-compatible syntax and functions. It is backed by highly extensible Python code, relying on <a href="http://sympy.org/">SymPy</a> for most mathematical tasks.</p>
 
       <h2>
       <!-- <a id="use-mathics-online" class="anchor" href="#use-mathics-online" aria-hidden="true"><span class="octicon octicon-link"></span></a>Use Mathics online</h2> -->