Newer RedHat OS versions?

Current RHEL is, I think, 6.4. Requirements say RHEL 5.X. Am I correct in understanding that 6.X is NOT supported?

That is correct. We have not certified 6.x. Generally speaking, we recommend using Ubuntu for Linux as that is our primary Linux testing environment.

Thank you for the quick reply. Since I am doing a new-from-scratch installation I can switch to either Windows or Ubuntu. Any preference from a support point of view? In doing our last install I found that I had to translate some of the docs from Windows to Linux. Is that a clue?

We do our development in Windows and it is also the primary platform for our automated testing. So it is the most comprehensively tested of the platforms we support. (Once automated tests are in operation, we determine which need to be ported to Linux.) For that reason, I would recommend Windows.