I have rewritten a few of the CSUOhio interactive optimization problems to use GeoGebra, as well as adding some additional standard calculus optimization problems. Because students often have the most difficulty first coming up with the function that needs to be optimized, each problem uses scaffolding to work students through the steps. The problems have been submitted to the OPL but for now can be found at
https://github.com/mathriddle/webwork-open-problem-library/tree/master/Contrib/AgnesScott/Riddle
or https://webwork.agnesscott.edu/webwork2/TestCourse2/ using Guest Login.
These are some of my first attempts at writing WeBWorK problems with custom answer checkers that try to identify common errors students might make, so any feedback would be appreciated.