Oh, I meant to ask about obfuscation mappings used when decompiling Minecraft, as in Mojang mappings or Yarn. But now that I've read bit deeper into that, I realised that they (or at least any that aren't Mojmaps) are tools created primarily to aid in modding the game, rather than just casually peeking into its internals. And I've only ever modded the game, hence why I didn't know better, haha.
Yes, he doesn't need to take the permission from anyone, including the user base of his platform, on which his business depends, and which is declining as a result of his decisions.