Tried the link again and it's working now - must have just been a glitch.
Without a lot of C programming experience I think that you will be struggling to make any headway into building Voice Activity Detection directly into Audacity (as a means of starting / stopping recording).
However, if you are thinking more of a non-realtime processing of recorded data for detecting areas of speech within a track, then I think you may have more success (though still very challenging). Audacity natively supports both Ladspa and Nyquist plug-ins. Without C+ experience, the Nyquist programming language is by far the easier. Nyquist is based on XLisp, and apart from the over-abundance of parentheses (you will need a text editor with parentheses matching) is a relatively easy language.
You can find information about Nyquist here: http://audacityteam.org/wiki/index.php? ... ist_Prompt