hey! i was an active Alpha Kappa Psi member when i attended the university of kentucky before transferring to eastern kentucky university, and i dont have any idea what YRS means. that must be something that varies maybe from chapter to chapter. I know that my omicron psi chapter has a small exec. board compared to a lot of other akpsi chapters. sorry for not being more helpful!
The Yellow Rose Society is a program that recognizes student members who make contributions to the Alpha Kappa Psi Foundation. If your university has a student member option for their alumni association that requires a small donation you can think of it being similar to that.
Derek is right. Another thing about joining the Yellow Rose Society is that they send you a pin after your money is sent it. Also, if several people from your chapter are part of the Yellow Rose Society it results in more ACR points. And, if you ever get to go to Success Institute they acknowledge you there also. It's a great thing, and a great way to give back to the fraternity if you can.