[MegaTrain]

Well, AI's (even hostile ones) will gladly trade you colonization techs, although sometimes you have to "sweeten the deal" by throwing in 50000 resources or something piddly like that.

You can even offer a SHIP trade for one of his colonization ships, and trade him an empty cargo vessel or something. Then you analyze the ship for the tech, spread his population around on the appropriate atmosphere worlds, and you're set to go.

I don't think I've EVER actually gained colonization techs through research. (Although unchecking "allow tech trades" hampers this greatly--you have to steal or trade ships, then)