I was listed on DMOZ, then removed..
I noted all the same things you see, same owners, same sites linked from different categoried of DMOZ..
I had a long discussion on DMOZ forum about all this and got nothing but abuse from them as well..
In the end here is the scoop of my findings after weeks of investigating this.
The higher ranked DMOZ gambling spots are controlled by a few editors only, and these editors do not looking out for the guidlines set by DOMOZ. I have a forum that at the time had more mmebers and features than ones listed in the chats and forums sections, the editor that added it even complemented it in an email (I still have). It was removed by a senior editor of the catgory and they do not offer any reasoning other than it should have never been listed go away.
After talkign with 2 current editors and an very well know ex-editor I found all my answer, none of thenm good.
A: The high ranking Gambling sections are for the intrests of some editors, not the users.
B: They do have a blacklist, and I am on it for any site I own or they feel im associated with as I opened my mouth.
C: Dmoz is corrupt, its grown so large and important that it was bound to happen.
Its just a link, really dont frett about not being there.
For a fun read check the DMOZ forum posts when I found my site delisted and the “Professional” responses. Note at the end I was pissed 
Allfreechips Dmoz thread
Enjoy
-Chris