They're offering an encryption product, not a service, an NSL would seem pointless unless they want to slap one at everyone who implements cryptography. and there's plenty of better ways for 3 letter agencies to obtain FDE keys. The Linux instructions just make it clear that your options and process vary per distro, if they're ditching the project I doubt they felt like writing piles more docs to describe every possible combination of loop-aes, dm-crypt, ecryptfs, encfs, luks, etc.