can i install pokerstars on ubuntu? If so, how?

If you're referring to the software from pokerstars.com, the answer is probably, but I'm not making any promises.

The site only offers downloads for Windows and Mac, but you can run many programs written for Windows with Wine. A guide to using Wine in Ubuntu can be found at:
https://help.ubuntu.com/community/Wine

An Ubuntu Forum post claims it's possible:
http://ubuntuforums.org/showthread.php?p=9007415#post9007415

Though the Wine application database (AppDB) gives it a Silver rating, suggesting there may be some minor issues:
http://appdb.winehq.org/objectManager.php?sClass=version&iId=2899

Make sure you grab the wine from the wine ppa. If the system needs wine 1.2 then use that instead.

You could contact pokerstars direct to let them know there is a need for a native client, they may make one if enough users pressure them. Is there not a flash client you can use in a web brrowser (or java)?

As stated install Wine first. Let either the Ubuntu gui find and install it or use the apt-get. I run Pokerstars using wine and it works. Not excellently but good and reliable.

Shark