There is no Solaris/SPARC application for Einstein@Home, this platform is not supported (yet). If you want to wait for it, you'll probably have to wait quite long. If you want to donate your CPU cycles until then, choose a (BOINC) project that already supports the Solaris/SPARC architecture.
BM
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Ok, my answer also was a bit unprecise (or incomplete). There is no Einstein@Home Application for the SPARC architecture (yet), neither for Solaris, nor for Linux, nor for Free- or OpenBSD (and what else OS may run on this hardware).
Linux on SPARC is rather uncommon, so you'll probably have to compile not only your own Core Client (which you already did), but also your own Application, which means you are limited to projects which make their source code available (like SETI).
BM
BM