I recommend spending some time reading the information on this link https://project-gc.com/forum/index?3.
Where this link can be found is under Tools - Challenge Checkers, then click on the Challenge checker forum button.
To answer the second part of the question, when I tagged a challenge checker I gained points. Developing challenge checker scripts also gains you points but I do not know what the point gains are since I do not write them. I only know about it.