Seems like the client on all poker sites are pretty much identical, except for the skin. What is it? Is it open-source?
To be able to answer your question as to which particular software you have seen in use, we'd need to know which site(s) you've seen that software on.
There are a couple of main ways that an online poker site operator may acquire the software which they use:
- Sole ownership
Examples: Pokerstars, FullTilt, PKR, PartyPoker
Some of the largest sites have developed their own proprietary online poker software over the years and they are the only site which uses this software. Often these solutions are considered the best experiences for the player/user - there's a reason that these companies can afford their own development and have survived in the marketplace against competition.
- Networks / skins / white label
Network examples: Merge, Prima/Microgaming, iPoker
Site examples: Carbon(Merge), BetVictor(Microgaming), Bet365(iPoker)
Some years ago, it was extremely common to have a central network which provided online poker software (amongst other things like Customer Service, Payment Processing etc.) to its members, who in turn then ran that software for their players/customers. In this model, the player pool was shared across the network, meaning that someone playing on Site A would see players from Site B, as long as both sites were on Network X. This was attractive to people wanting to start an online poker business in those boom days as it provided the ability to buy a "business in a box" and generate revenue immediately without having to do a lot of the hard work a startup would otherwise have to (building infrastructure, a player base, etc.)
To answer your specific question about open source poker software, I don't believe there are any real-money sites using an open-source client, but I may be wrong and just haven't been able to find them.
Nowadays online poker is extremely popular casino card game played throughout the world. It is not just entertainment and hobby, but it is also a kind of sport, business, and way to earn money. The industry accounts 40 million regular players worldwide. By the end of 2017, according to H2 Gambling, the market volume of online poker will exceed 6 billion dollars.
To meet various players’ requirements, poker rooms try to improve their service, offer profitable bonuses, organize different tournaments and run promotional campaigns. However, they cannot work without a proficient poker software, it is a keystone.
Only the biggest poker rooms develop poker software themselves (for example, Poker Stars, 888poker). The others buy poker software from software development companies as:
- EvenBet Gaming,
- Connective Games,
- Betconstruct, and etc.
The functionality of the biggest rooms is handy and catchy, that’s why the most of the providers offer similar options and games types. It is the main reason why different poker rooms, even from different corners of the planet, look identical and have the similar structure, including:
- The lobby;
- Types of tables, poker games and tournaments;
- Types of pots;
- Numbers of players in the poker room;
- The game status of the player;
- During the game: online chats and statistics.
It is a basic structure, but to the joy of the poker room owners’, the providers make their solutions customizable. Therefore, in such way poker rooms may choose and adjust any package of online poker games depending on their own wishes and tastes. They can customize:
- Design and skins. The customizing basics – the casino or poker room looks. Some companies offer their clients to create specific tables design, or change animation, add 3D graphics elements, even create a new main lobby elements layout. All of these instruments allow giving poker room a unique look.
- Games and tournament types. That’s a very important option for local markets and specific audiences. At EvenBet Gaming, by the customer’s demand, such locally popular games as Teen Patti (Indian and Southeastern Asian favorite) or Pai Gow poker (adapted Chinese domino game) were created.
- Game features. Now the providers can implement extended statistics modules, various instruments to increase users’ loyalty and retention – from notifications to waiting lists, payment options, and more.
For more information, how the poker room can be customized, see here: http://evenbetgaming.com/why-should-you-choose-customizable-online-gaming-solution/.