@paradox26- reposted again

There are numerous ways to have spells count as the opposite source (arcane as divine, divine as arcane), especially from Dragon Magazine. Are those ways allowed for counting as casting the opposite source for PrC requirements?

If it helps, I was planning on using Southern Magician to use Eldritch Theurge(or the other one. I can't remember the name offhand, but the arcane one. I'm taking 10 levels of the divine one and don't want to hammer out an epic progression) to progress my Cleric casting while advancing Warlock.