Yes men, RMXP run in 98, I have win XP and 98 and the program run perfectly, Zero Problems. (The games also run eh)
The RMXP is called XP because the color deep is 16-32-64 bits of video, and the olders Pc's only had a maximum of 8 bits, obviusly if you have a modern Pc with 98 Rmxp will run, if you have an older pc the software doesn't run...