Red Hat dropped support for the Sun Microsystem's Sparc chips platform already in 2000.
You may have more luck with Debian http://www.debian.org/ports/sparc/ or Slackware for Sparc http://www.splack.org/.
To the link you advised. I found that Sparc still support in Red Hat.
12.5 RedHat Linux.
The latest RedHat Linux distribution for the SPARC architecture is the 6.2; you can download it at http://www.linuxiso.org/download.php/243/zoot-sparc.iso for example.
There exists a mailing list about Linux and RedHat on SPARC Processors, you can access it there: http://www.redhat.com/mailman/listinfo/sparc-list