See here: https://forums.galciv4.com/505410/tips-tricks-new-to-gal-civ-iv - "You need to change a citizen into a 'trader' in your planet screen in order to get a license to complete a trade route. "

BTW, I reported a bug where if an AI civ establishes a trade route with one of your planets, it counts against your trade license count. So I had 2 routes and 2 trader citizens, then an AI set up a trade route with me. To establish my 3rd trade route I had to create 2 more trader citizens.

Holy Crap!   I didnt know this.   I thought the only way to add trade licenses was researching trade techs!

This will allow me to get my money situation stable more quickly.