There is currently a no tech trade option. It's great. It ramps up the difficulty quite a bit because it forces you to really think about what techs you're researching, and doesn't allow you to abuse the ai through diplomacy, especially when playing with a lot of opponents.
There has been a call for furthur restriction of tech exchange by way of either espionage or invasion by others that I'd like the ooportunity to elaborate on.
First, in terms of difficulty, the current method of winning a masochistic or better game (with no real cheese involved) is to simply start an early war and pick on someone who is relatively weak before they build a decent military. Once that war is over, after invading all of his planets you will likely have stolen several decent techs that will be used in your next war, and from there it snowballs. Without being able to steal techs the first war would go the same as always, but after that you'd be behind techwise, and probably by a large margin. Suicidal games shouldn't be winnable without a great deal of diplomacy, exemplary strategic thinking, and a good dose of luck. Rush tactics have their place but with tech stealing involved they have long term strategic value as well. There are also cheese tactics involving invading a race and then giving the planet back just to invade it again, but I'm not talking about removing dumbness from people that want to ruin their games like that. Even using legit tactics, tech stealing gives a greater edge than it should.
Secondly, in terms of modding, which is why I placed this post here, there has been desire to create mods that give certain races their own technologies. However, with tech stealing in place there is no way to keep other races from learning techs they aren't supposed to. So it allows a loophole to get around a mod restriction and presents a roadblock for many mod designers, myself among them, and we'd like the option to turn it off, both by toggle on the main screen, as well as by scenario editting.
I appreciate the great work you've done so far, and your recent update looks great (specific thanks for the lost production and save game bug fixes, big time

). Sorry if I sound like a nag, but there's always something that could make the game better. I try to keep my suggestions simple and to the point, even if I can get a little wordy on the subject.