If so, why should nations give away their expensive research that potentially give them an edge either military or commercially?
Personally I almost never traded technology when I played civilization, let alone give it away!
Yes. The answer is unequivocally yes. Your country will benefit vastly more from the research being freely available than other people having a better world on your dime will disadvantage you.
And here's the thing. Other countries face the same calculus. Scientific research brings the greatest return on investment of anything ever. It's why we have electricity and computers and satellites and penicillin. At the national level you can pay for it and give it away and still come out ahead regardless of what anybody else does.
Since every country benefits from doing it by more than it costs them, everybody can "cooperate" by doing research and giving it away without having to worry about anybody else defecting -- because defectors can't hurt you, they can only not help you. The sooner everybody realizes that the sooner everybody can choose to cooperate and the better off the whole world will be.
And the returns when every country publishes research for free are... large.
Good point about the current situation.
"We have 25 or so years invested in the work. Why should I make the data available to you, when your aim is to try and find something wrong with it. "
- And especially when public policy often demanding massive input from the taxpayer depends on it.
This is one of the easiest ways to manipulate the AI players...