The code is MIT licensed if and only if the copyright holder - not the author of the story but respectively Box or Uber - explicitly made it MIT licensed. Without a legally binding commitment from these companies, a "license.txt" at the repository can't make it MIT licensed, all it means that the author is lying about its license. He doesn't own the code (despite writing it) so his "permission" is worse than worthless (by being dangerously misleading) without an explicit blessing by the company - even an implicit "we probably don't care" doesn't cut it.