If someone asks if you support a technology, and you can't tell if it's even installed, perhaps the proper response to the question of whether you support this, is 'no'. Do you have any other XSLT engines installed, like Xalan or libsxlt? Will installing Sablotron conflict with the existing setup? Not all XSLT engines give the same output.
Sablotron is an XML/XSLT C library. I don't know if it's part of any default installation. I'm sure it's a readily obtainable RPM package for RedHat, but how will Sablotron be called? If it's needed within a PHP script, you'll also need to know how to recompile PHP with the Sablotron libraries:
Eric J. Bowman, principal
Bison Systems Corporation coming soon: a new sig!
I'm just a poor, unfrozen caveman Webmaster. Your new 'standards' frighten, and confuse me...