toad, taiwan wasn't a part of that arrangement from what i've heard (from charles h. shapiro, one of my physics professors and los alamos alum), but israel did test it's nukes in south africa*. they colaborated*, with israel and both countries developed nukes - israel contributing it's stolen info* from the us and south africa contributing a place to do the dirty work away from prying eyes.
(*it is speculated)
s.a.'s program was developed when whites held power there and presently nelson mandela has been extremely anti nuclear. the stated aim of the original south african nuke program was one of deterrence anyway, and despite south africa's record on human rights, they never planned on using it against an enemy but rather to keep restless african neighbors at bey. they are one of the countries that say this and scholars actually agree.
in fact south africa is often held out as the shining example of a country that has successfully dropped in's nuclear program, and they stand as the only country to start such a program and then abandon it volutarily.
some speculate the south africans were not able to keep close enough controls on their facillities and weapons and dropped it as a safety measure but i applaud them all the same.
it's speculation again but ask anyone in science and see what they tell you or ask them how much they were offered to help
a lot of interesting stories live because of this arrangement...