In the
showthread template there is this code:
Code:
<vb:if condition="$show['closethread']"><span>+</span> {vb:rawphrase reply_to_thread}<vb:else />{vb:rawphrase closed_thread}</vb:if>
So
Code:
<vb:if condition="$show['closethread']">
is the condition but if it's TRUE the thread is OPEN, if it's FALSE the thread is closed... at least that is what it looks like to me.