I'm playing as a custom race that is using the Terran tech tree. When I go to the trade window I see techs listed on the left hand side (where the techs I have and can trade) that I haven't researched and aren't in the Terran tree. The screen shot shows the tech Mental Exploitation, which is in the Drengin tech tree, not the Terran tech tree. And no, I haven't traded with the Drengin for it, the Drengin are not in my game.
As another example, I've researched the Federalist Party tech to get the +20% economic bonus, but the tech listed in the trade screen is Slave-Master Party, which gives the same bonus but is a Drengin tech.