OK I'm going to take this CMS for a spin. Downloaded the zip, extracted it, created a symlink the symlink

concrete5 -> concrete5.3.3.1/

did a chmod of 755 initially then 766 (after the install puked) on the entire concrete5 dir

owner and group is correct for my web environment but when I hit the page to start the install I get -

Warning: session_start() [function.session-start]: open(/var/tmp/php/sess_0c50590981a78c6fdd1b32cd0c4cca1f, O_RDWR) failed: Permission denied (13) in /xxx/concrete5.3.3.1/concrete/startup/session.php on line 18

Then I also get -

Support for C5 Request URLs
Concrete cannot parse the PATH_INFO or ORIG_PATH_INFO information provided by your server.