OK so we get back to the OT or at least the spirit of the OT as this could be an interesting thought experiment.
Ok say your Server Admin has banned all travel out of the overwold on pain of Ban. No Nether, No End, No TF, No Mystcrft, No DimDoor..... you get the idea. Overworld only.
So hypothetically how would you go about getting the Netherack? Bonus if we can find a realable way to get the other off world matirals too.
My brain screams UU-matter. You would need to create the glowstone needed from IC2's hidden recipe (redstone and gold dust).
But for the sake of the thought experiment, I'd go for the Tome of Alkahes- wait, no, requires a Wither Skeleton Skull and a netherrack as a pattern, as well as some other Nether stuff.
Only other thing I can think of would be pulverizing nether ores from the MFR laser thing.
Unless some Ars Magica towers include netherrack... Which wouldn't be renewable. Could provide the pattern for Alkahestry, but you'd still need the wither skull.
Perhaps Ars adds some spell that can convert something into netherrack?
Custom Recipes Mod probably isn't OK, either.
I doubt that adding renewable Netherrack is high on any modder's list, seeing as there is so much of it.
GregTech has no method of turning netherrack dust back into netherrack. There's no way to produce the stuff either, aside from macerating netherrack or scrapboxes.
Also, is MineChem allowed, since it's not updated to 1.5?
Netherrack seems to be a mix of Silicon, Oxygen, and Iron. Silicon and Oxygen are easy (decompose cobblestone), while Iron, I suppose, could be provided by bees.
Speaking of which, it doesn't look like there are any bees that produce netherrack directly. I could be wrong, though.
*looks up Netherrack recipes in NEI, current recommended Ultimate pack*
The Scrapbox Lottery can provide netherrack, as someone mentioned.
Ooh, cooking cobblestone in a Soul Forge produces Netherrack... You'll need soul sand and glowstone for the fuel, though. MFR Sludge Boiler connected to a Harverster provides soul sand (occasinnally), glowstone can be obtained from IC2's recipe and bees producing redstone and gold. If I remember correctly, the bees that make glowstone directly are in the Nether branch, so that won't work.
The Fire Basin from Xycraft shares netherrack's essential property of eternal fire- but requires red xychoridite, which isn't renewable.
Oh, it also seems that (with GregTech in 1.4.7) pulverizing nether ores of Power Crystals gives the same bonus product that pulverising their overworld counterparts does.
In 1.5.2 without Nether Ores or GregTech, the pulverizer doesn't even recognize Nether Quartz Ore or either of the Tinkers Construce nether ores.
All told, the best choices (in my opinion) look like chucking iron derived from bees (or nuclear fusion, or one of MineChem's various exploits) into MineChem, or throwing lots of bee products into a Soul Forge.