You can read more about Open edX’s ORA feature here:

http://edx.readthedocs.org/projects/edx-partner-course-staff/en/latest/exercises_tools/open_response_assessment.html

And the next generation of ORA (which is called ORA2) here:

http://edx.readthedocs.org/projects/edx-ora-2/en/latest/  

(please note that this is more developer documentation than end user documentation, but it should give you a sense for what is possible)

If you’d like to test-drive Open edX, we have a service that will give you a free fully-functional Open edX site to play with for 24 hrs. You can go here (
http://openedx.appsembler.com) and click on the Free Trial button.