Vintage Minor Register

Does anyone know what these are? They come up when accessing individual vehicles via the DVLA website.

For example, if the website states liability is December 2011, does that mean that the vehicle is currently taxed, or is this the theoretical taxation/sorn date? or something else entirely?

I think it is the date on which the vehicle road tax has to be renewed or the vehicle put on SORN.

however, it doesn't state whether licensed or sorn which is the norm....

I have just tried my tourer and the liability date appears to be the licence date and licence not due means it is currently licensed