SOURCE literally has no relevance or function in the game itself.
One of the early quests from Divine Divinity. Pulled from the Wiki.
Find a Cure for Simon/Verlat.
Upon speaking to Goemoe, who cares for Simon or Otho, who is responsible for Verlat the Hero is informed that they are unable to treat their patients due to the connection to the Source being broken. Neither Goemoe or Otho can use the last Healing gem as it would against their code, thus "choosing who should live or die".
So yes ... Proof. If nobody had access to Source, then nobody would have access to magic as per the OP's viewpoint. Yet Magic did still exist in the game. But the connection to the Source was broken at the time.
I remember trying to find a way around that dilemma.
Also DOS 1 had that quest return with the "only 1 healing stone but 2 people". They constantly referred to Sourcerors and Wizards as separate in DOS 1 as well.
That makes it quite clear that Magic and Source are indeed seen as Separate Entities.
