Why does the DDJ-FX4 - a beginners controller - require a VDJ Professional licence @ $19.00 per month?
You should probably ask VDJ about that.
It is because entry level controllers are also used for smaller gigs on just for practicing at home. For that, you will need a VDJ Pro license.
Do it, it is money well spent if you are a DJ and you are also helping a small company. Not corporation.