YafaRayforXSI is a project mainly written in C++ and C, it's free.
YafaRay Exporter for Autodesk Softimage
YafaRay Exporter for Autodesk Softimage.
Download addon from http://static2.yafaray.org/YafaRayforXSIbeta_0.1.zip or.. https://github.com/downloads/povmaniaco/YafaRayforXSI/YafaRayforXSIbeta0.1.zip
See the wiki page (wip), how to install and configure the addon.