I FIGURED IT OUT.
Okay, so, you know how RTD's Time Lords were striving for the "Ultimate Sanction," right? Okay, okay, hear me out:
The Ultimate Sanction was basically the destruction of the universe and TIIIME ITSELF (insert copious amounts of saliva) in order to cause the Time Lords to "ascend" to a higher plane as beings of pure consciousness, yeah?
The Alterrans - or Ancients - of the Stargate universe were beings who looked much like humans, but managed to "ascend" to a higher plane of existence, refusing to intervene in the lower planes. The Ori were basically Ancients with a 'tude problem, intervening to make people worship them.
HEY, NICE HEADDRESS. Didn't I see that in Gallifrey's Vogue?
Therefore, using cracked out fandom logic, I postulate that the Ori are the Celestial Intervention Agency in a universe/timeline where the Time Lords completed the Ultimate Sanction, discovered they couldn't survive in their current form, and needed a way to carry on as they were without the return to corporealness. THUS:
1) They "cracked" through into our universe.
2) They created the Silence to manipulate mankind into serving them - without mankind figuring it out. (From The Book of Origin: "Where there was silence, the Ori brought the gift of speech.")
(POTENTIAL SPOILER FOR S6: Also, doesn't a certain
someone look terribly a lot like a
Prior of the Ori, here?!)
Remember - you heard it1 here, first! ;)
EDIT: Ooh, ooh! And the Ori's Celestis = the EDAs Celestis! (Okay, I'll stop...)
1 "It" being a spectacular, first class load of bollocks, probably, but hey. I'm allowed to get myself carried away once in a while. I have the Internet.