I've subscribed to JFD's Calvin Coolidge mod and looked through the files. It seems he's used this code:
CREATE TABLE IF NOT EXISTS
Project_TraitType (
ProjectType text default null,
TraitType text default null);
INSERT INTO Project_TraitType
(ProjectType, TraitType)
VALUES ('PROJECT_JFD_DEREGULATE_BUSINESSES', 'TRAIT_LEADER_PROJECT_JFD_DEREGULATE_BUSINESSES');
I attempted to use this in my own solution, substituting his project and trait for mine, and giving my leader the right trait. However, it didn't work. All civs are still able to see the projects in the tech tree as unlockables. Is there something I'm missing? Something to make the game read the new table as a new TraitType?
(Of course, full credit is to be given to JFD for the code)