Israel & Singapore are Security Cooperation Participants in this project; as the article noted, they each contributed $20 million towards the project. (The UK, the only level 1 partner, contributed $2.5 billion, or 10% of development costs). It would be helpful to know what modifications the other participants at various levels are permitted to make to the aircraft.
I worked for a defense contractor that was competing for this project; we were very disappointed when Lockheed was selected as prime contractor although of course we did get some work as subs.