Board Thread:News and Announcements/@comment-26888709-20171224002654/@comment-25330335-20171224010106

That depends on technical implementation (is the mod statically linked with the actual game or not). And even still, they can use API's that have certain laws binding their use. Mojang is alright with mods, so it's really Mevans' call as to whether or not submods are allowed.