The reason .org was created was for non profit organizations. But anyone can register them nowadays.
Exact, anyone.
And there is so great websites (gambling) that are .org.
I still wouldn't recommend a .org for gambling though.
OK, that's you, but not the owner of betwin.org whos making money with his biz.Domain have to be nice and short, so people can remember it.
.com, .net, .org or even a second level domains like .co.in are good if your website concept is fine.
casino.org
poker.org
winabet.org
betwin.org
ebet.org
footballbet.org
betonline.org
say again and you'll be funny after this post
What's funny of my post? It was just my opinion.
All the sites you linked are informational (affiliate) sites, not actual gambling sites.
Since we like to laugh at each other, did you ever think why you could still register these new domains? They aren't anything special.