Updates footer language around github link

bookwyrm/templates/layout.html

@@ -214,7 +214,7 @@
                 </p>
                 {% endif %}
                 <p>
-                    {% trans 'BookWyrm is open source software. You can contribute or report issues on <a href="https://github.com/mouse-reeve/bookwyrm">GitHub</a>.' %}
+                {% blocktrans %}BookWyrm's source code is freely available. You can contribute or report issues on <a href="https://github.com/mouse-reeve/bookwyrm">GitHub</a>.{% endblocktrans %}
                 </p>
             </div>
             {% if site.footer_item %}