It is not limited to Magecraft, and will trigger every ability that says "Whenever you cast/copy and Instant/Sorcery spell, do X" an additional time.
The easiest way to it is to think about it as a
Panharmonicon (or
Yarok, the Desecrated), if you're familiar with this card, that double cast/copy triggers instead of ETBs.
Also note that Veyran's own ability will always trigger twice, so every instant or sorcery you cast or copy will give them +2/+2.