Functionally, this patch is similar to the RacialTech patch. Where that patch allows for an alias file, for those who may have renamed the races, this patch doesn't require one. It introduces four hardcoded tags:
NoSteal: Prevents the tech from being stolen by spies.
NoTrade: This tech will not show up as a trade option (or for demand, or any other diplomatic avenue).
NoCap: Prevents the tech from being acquired by capturing a planet.
NoRandom: Prevents the tech from being granted via a random event or special.
This tags can be used separately or all together. Using all of them effectively bars a race from aquiring the technology unless it can research it.
The tags get applied to the 'Sort_Tag' column of TechTables.txt. For more precise details about how to add them, see the RacialTech patch.