This is partly inspired by the definition of magecraft in the wiki:
It says nothing about whether something is Top Secret, or even Above Top Secret. Depending on how you look at it, it could be 'anything the Collective Unconscious of Earth knows how to do' (and given the lack of interest Nasuverse magi have shown in SCIENCE!, the individual magus doesn't seem to need to know how it works, just how to get the World to do it for them). That works well with the idea that magecraft is psychic manipulation of matter and energy, which is certainly possible in Stargate, while True Magic is working out how to do something beyond what is currently known, which the World tries to prevent.
Depending on how you look at it, the two times Jack got <a href='http://stargate.wikia.com/wiki/Repository_of_knowledge' target='_blank' rel='nofollow'>grabbed by the Ancient head-sucker</a> might count (it doesn't so much matter that he doesn't remember, the knowledge would still be in <a href='http://typemoon.wikia.com/wiki/Akasha' target='_blank' rel='nofollow'>Akasha</a> - though depending on how much knowledge Akasha kept from Jack, this could be really unbalancing), as could Jacob Carter blending with Selmak, or even Sam getting possessed by Jolinar - regular Goa'uld would be less inclined to share how things work with their hosts. The stuff they actually know how to build from scratch, rather than from stolen or purchased parts, certainly does. As things suddenly become possible or easier to do, they're going to start wondering what's going on, and some magi will start investigating.
The <a href='http://typemoon.wikia.com/wiki/Age_of_Gods' target='_blank' rel='nofollow'>Age of Gods</a> is an issue, but in this timeline, it could be something cyclic, (or something that seems cyclic, but is actually more complicated), rather than linked to population, as the modern magi believe. Ra arrived and left during the low part of the cycle, and <a href='https://secure.wikimedia.org/wikipedia/en/wiki/Gilgamesh' target='_blank' rel='nofollow'>Gilgamesh</a> lived during the high part.
Alternatively, magic circuits may have been a gift from <a href='http://stargate.wikia.com/wiki/Merlin' target='_blank' rel='nofollow'>Moros</a>, <a href='http://stargate.wikia.com/wiki/Janus' target='_blank' rel='nofollow'>Janus</a>, or one of the other Ancients who came to Earth, but they could only make so many before the others stopped them, and these same circuits have been passed on over and over through the ensuing millennia. Of course, if the knowledge of how to make more is in the Repositories, Earth's magi may now be able to make more. <a href='http://typemoon.wikia.com/wiki/Emiya_Shirou' target='_blank' rel='nofollow'>Shirou</a> was able to make temporary magic circuits from his own nerves (which was a bad idea, but he didn't know any better), so making new permanent magic circuits could be possible already (there's an idea for that already, on SB.com). If this path is taken, the problem of magical strength being a limited resource (the more magi there are, the less powerful each one is) is itself caused by the limited number of magic circuits, and thus is no-longer a problem. Yes, this could be very unbalancing, but I didn't say how difficult/expensive it would be to make more circuits.
So, thoughts?
Magecraft is the ability to reproduce what can be scientifically realized regardless of time and funds. The limits of Magecraft have changed with time, as science evolved and miracles from before became technically possible through science.
Depending on how you look at it, the two times Jack got <a href='http://stargate.wikia.com/wiki/Repository_of_knowledge' target='_blank' rel='nofollow'>grabbed by the Ancient head-sucker</a> might count (it doesn't so much matter that he doesn't remember, the knowledge would still be in <a href='http://typemoon.wikia.com/wiki/Akasha' target='_blank' rel='nofollow'>Akasha</a> - though depending on how much knowledge Akasha kept from Jack, this could be really unbalancing), as could Jacob Carter blending with Selmak, or even Sam getting possessed by Jolinar - regular Goa'uld would be less inclined to share how things work with their hosts. The stuff they actually know how to build from scratch, rather than from stolen or purchased parts, certainly does. As things suddenly become possible or easier to do, they're going to start wondering what's going on, and some magi will start investigating.
The <a href='http://typemoon.wikia.com/wiki/Age_of_Gods' target='_blank' rel='nofollow'>Age of Gods</a> is an issue, but in this timeline, it could be something cyclic, (or something that seems cyclic, but is actually more complicated), rather than linked to population, as the modern magi believe. Ra arrived and left during the low part of the cycle, and <a href='https://secure.wikimedia.org/wikipedia/en/wiki/Gilgamesh' target='_blank' rel='nofollow'>Gilgamesh</a> lived during the high part.
Alternatively, magic circuits may have been a gift from <a href='http://stargate.wikia.com/wiki/Merlin' target='_blank' rel='nofollow'>Moros</a>, <a href='http://stargate.wikia.com/wiki/Janus' target='_blank' rel='nofollow'>Janus</a>, or one of the other Ancients who came to Earth, but they could only make so many before the others stopped them, and these same circuits have been passed on over and over through the ensuing millennia. Of course, if the knowledge of how to make more is in the Repositories, Earth's magi may now be able to make more. <a href='http://typemoon.wikia.com/wiki/Emiya_Shirou' target='_blank' rel='nofollow'>Shirou</a> was able to make temporary magic circuits from his own nerves (which was a bad idea, but he didn't know any better), so making new permanent magic circuits could be possible already (there's an idea for that already, on SB.com). If this path is taken, the problem of magical strength being a limited resource (the more magi there are, the less powerful each one is) is itself caused by the limited number of magic circuits, and thus is no-longer a problem. Yes, this could be very unbalancing, but I didn't say how difficult/expensive it would be to make more circuits.
So, thoughts?