Since MIT Lincoln Laboratory's establishment, the scope of the problems has broadened from the initial emphasis on air defense to include programs in space surveillance, missile defense, surface surveillance and object identification, communications, homeland protection, high-performance computing, air traffic control, and intelligence, surveillance, and reconnaissance (ISR).
Lincoln Laboratory conducts research and development pertinent to national security on behalf of the military services, the Office of the Secretary of Defense, and other government agencies. Projects focus on the development and prototyping of new technologies and capabilities. Program activities extend from fundamental investigations, through simulation and analysis, to design and field testing of prototype systems. Emphasis is placed on transitioning technology to industry.
Essentially, the Lincoln Lab is one of several labs that are part of a strategy to make best use of creative people (who can think up things, but don't necessarily want to productize/weaponize them), industry (who can productize/weaponize things, but don't want to be part of a war effort) and military.
To see why they would not hire non-US citizens, consider the first author of the "Steal this Movie" paper, who now works at a Chinese university (presumably on similar problems to the ones that people in LL and at UCSB are tackling).
Not a bad trade.
Just wanted to say thank you: just being aware of limitations like this and letting people know up front makes it a whole less annoying. Also the circumstances makes it understandable.