There's also code that github themselves uploaded which they were permitted to do under the open source licenses in the mirrors user. I know some of these repos

There's also code that github themselves uploaded which they were permitted to do under the open source licenses in the mirrors user. I know some of these repos have since been moved as the authors became active on github (e.g. mirrors/linux is now torvalds/linux, indicating Linus has control of it even if it's a read only mirror), but I'm sure there's a few of them remaining.