Thank you all for the suggestions.
I just upgraded to 11.4_x64. Unfortunately Gaussian v.03/09 software installs only in SuSE Linux 9.3, 10.3, 11.4 or SuSE Linux Enterprise 11 SP1. Also the Gaussian remark "SuSE versions specified for AMD64, EM64T, IA32, IA64, and IBM Power systems refer only to the unmodified, unpatched original media/ISO image distributions as released by the vendor". So I have to live with this for a while, unless you guys know another way. But this is not important now.
Back to your questions:
I installed ruby with Yast from the ISO image DVD as downloaded from the net.When slecting ruby it installs all dependecies automatically as they are all available on the media.
I am using configure in a program called psi3 (an open-source suite of ab initio quantum chemistry programs -http://www.psicode.org/). It seems that it is very simple to install it except for the ruby issue.
I tried the suggested recommendations (except upgrading to Suse 12.1). I didn't try to explore the subject going to www.ruby-lang.org
, maybe it helps. Anyway, the 'missing files' ruby.h and libruby-static.a are effectively available in their directories. I don't understand why the symbolic link does not work.
Any additional help is welcome.