But this is something that will not end well at all.
I also saw this at Gen Con and wondered at first if this was an old TSR book that never saw the light of day or something new.
This issue here of course is using a trademark, "Advanced Dungeons and Dragons" which is specifically prohibited by the OGL.
There are more discussions going about here:
Even people that don't like new D&D or WotC see this as a bad move.
There are a lot of problems with this, mostly effecting the OSR publishers wishing to reach out to new audiences.
This is one to keep an eye on.