Who would ban Mundungus other than Aberforth?
And do we know that Aberforth doesn't own the Hogshead?
The book said he worked there, but didn't say whether he also owned it.
We haven't seen anyone else there.

Dumbledore mentioned (I forget where) having a connection to the guy,
but neglected to mention that he was his brother.
The whole thing is very vague and shady.