The orientation of VOR antennas is fixed at the time of installation and cannot be changed so the radials refer to the magnetic north which existed when installed.
Note that this refers to the LOCAL magnetic field which may or may not be significantly changed by the magnetic pole wandering as described in the article.
Not the case. All VORs can be adjusted. More modern versions with just the tweak of a screwdriver or the press of a few keys on a laptop, older ones sometimes required large spanners and a hammer. The practice in the UK and most states is to adjust them during flight inspection to minimise the predicted difference over the period to the next expected flight inspection. For DVOR that is 5 years in the UK.