Files locked on Windows

...

<New id="myWebAppContext"  class="org.mortbay.jetty.webapp.WebAppContext">
  <Set name="contextPath">/</Set>
  <Set name="war">./webapps/fredapp</Set>
  <Set name="copyWebDir">true</Set>
  .
  .
 </New>

It seems one can also configure the default jetty Servlet directly in the web.xml. For example:

<web-app ...>
...
<servlet>
    <servlet-name>default</servlet-name>
    <servlet-class>org.mortbay.jetty.servlet.DefaultServlet</servlet-class>
    <init-param>
      <param-name>useFileMappedBuffer</param-name>
      <param-value>false</param-value>
    </init-param>
    <load-on-startup>0</load-on-startup>
  </servlet>
...
</web-app>

...Altough, it may completely redefine the default servlet configuration (not sure about that, if anyone can confirm). You could anyway simply extract the webdefault file as explained above, and copy-paste th complete default servlet definition in your web.xml, changing that useFileMappedBuffer parameter to false.