The MPL license
under which SEB is released allows this, given the conditions listed in the license. This includes that you have to release changed SEB code parts under the same MPL open source license and have to attribute the original developers. But don't forget, your developers will have to work constantly on merging changes and bug fixes from new SEB releases into your own version. You will also have to do your own testing for any platform you want to support. In most cases this won't be very efficient. It would probably be more reasonable to contribute code for features you require to the SEB project and use the official SEB version with your exam system.