Forum:Vanilla Edition?

I've seen reference to a "Vanilla Edition" released alongside a particular disc, what is this referring to? For example,

Time Crash
 * Released in a vanilla edition alongside Voyage of the Damned on 10th March 2008.

Does this refer to the "to be continued" type episodes? Is it a specific Dr Who reference, or is it used elsewhere? Thanks for your time, my searches didn't turn much up.