Yes, It does require an ante

All Oklahoma casinos do, unless the casino is offering a special promotion. Many casinos offer certain days of the week or a whole month with "no-ante". Riverwind requires a .50 cent ante if you bet $100 or less...if you bet more than $100, the ante jumps to $1!!
Check out our new website (Dead link: http://www.OklahomaCasinoGuru.com) You can find all the casinos in Oklahoma and many featured casinos that will tell you everything about the casino. Riverwind is not yet a featured casino, but we are in talks with them to make that happen! We are Oklahoma's casino guide.
I can tell you that Fort Sill Apache Casino...which is a featured casino, is going to have a $250,000 tournament in November. 1st place gets $100,000. For all the deatils and breakdown, go to out site. (Dead link: http://www.oklahomacasinoguru.com) or (Dead link: http://www.okcasinoguru.com)
Hope this answered your questions! Best of luck