More seriously, WTF does the embedded operating system on the rifle have anything to do with this? User interface? Well it might be easier to program, but it's not integral to the device. ultitasking? Also no. While useful it's not necessary. Memory management? You probably don't have gigabytes of RAM and terabytes of disk space. So Linux has nothing to do with the core operation of the long range targeting on the rifle.
Lack of a blue screen.
This is yet another example of a stripped-down Linux getting buried in some device that you normally wouldn't even think of having an operating system.