System requirements on OpenSees website does not specify CPU, but it would be very unusual for an application to only work on Intel-based systems. There are exceptions though 'cos I remember reading some years ago that Photoshop (don't know what version) wouldn't run on AMD CPU, so I made sure my new PC at that time was Intel-based.
For 100% confirmation though you would need to contact someone who is actually using that specialised software.