The current libspf2 ebuild is really old : it is for version 1.0.4 The latest libspf2 version is 1.2.5 and is stable on many architectures. Just cp libspf2-1.0.4.ebuild libspf2-1.2.5.ebuild is enough and a change of KEYWORDS to "~x86 ~ppc" I've tested it on ppc successfully
lbspf2-1.2.5 is in portage.