I have compiled yacas on my Athlon64 and it runs; plotting via gnuplot works too. One minor issue: on-line documentation (?) gives a view on my home directory instead of displaying the yacas documentation pages.
It is quite likely that the on line documentation is broken too in other architectures. yacas expects the html documentation files in /usr/share/yacas/documentation while they are stored in /usr/share/doc/yacas-1.0.56/html. A symbolic links solves the problem.
in CVS now, thanks!