At the beginning, I would like to say that you did a great job in creating Web-CAT. That kind of systems are so much helpful for teachers and students.
Since a few years, I also teach students of programming languages (and programming itself) at Poznan University of Technology in Poland. Last year, I decided to develop and deploy an automated grading system and with students I started the project from the beginning (now we are using quite simple system), however developing another similar system is not the best idea. Therefore, I would like to get involved in Web-CAT project.