After installing the demo I just get a segfault

May I ask which Linux distribution and version you are using?

This happened to us, also. Redhat 7.3, when we installed 5.1r3. We can still use the 5.0 we had downloaded for a demo on the 7.3 machine, and we're upgrading to White Box 3.0, where we've tested 5.1r3 and it works fine.