I wouldn't count workshops as 'fringe' - or indeed, anything else which was organised as a part of the Festival. I think a Festival is made up of much more than concerts - it includes outdoor dance, indoor dance, organised singarounds, organised particpatory musicians sessions, tents with crafts in + anything else the organisers have laid on.

The fringe is anything above and beyond that which is taking place in similar vein, I suppose, to complement the organised activities - presumably 'started' rather than organised by festival attenders or residents of the locale.

If artists are involved in Meet the artist sessions, it will (usually) all have been discussed and arranged - either directly with the artist, or via their agent - before the event. I wouldn't consider these to be 'fringe' - just events of a smaller, more intimate nature.