I'm guessing you're not aware that Texas Hold'em is a common, very popular form of poker here in the US. It's been around for awhile I think, but I only learned of it myself last year or so. They have tournaments in Las Vegas, and even
air it on TV like it's some kind of sport in the US (it's actually very interesting -- much more so than golf, I'd say). It's sort of like all the millions of software versions of basic casino games or solitairre. They're pretty much in the public domain as long as no one's individual trademarks are infringed upon, like a particular casino's name. The developer could always license the casino's name (or Telltale's even), and work that into their own version.
As it is, I don't think Majesco's DS game will be based on Telltale characters, although it would be very cool if it were.