I'm with the OpenMW project and we are making a reimplementation of the Morrowind III engine which will allow for improved graphics, AI, and combat. It's almost been 4 years since OpenMW began.
We are only in the initial planning phases for developing an open sourced version of the construction set, but I thought it would be wise to ask if Bethesda could simply open source the existing one. Why recreate the wheel right? I know that the Morrowind engine cannot be open sourced because it has uses proprietary middleware, but is the same situation true for the CS? If you do make it open source it will be a huge help to our project and the community. Thanks for your time.