This may be of assisance - From Dave Schroeder's macmini page (albeit relating to 10.3):
"some Mac OS X Server CDs may not be new enough to boot Mac Mini. Therefore, the preferred installation method would be to install Mac OS X Server on a machine which the CD can boot, update to Mac OS X Server 10.3.8 once released, and clone that installation to the Mac Mini (using a tool such as Carbon Copy Cloner; or, boot the Mac Mini in target disk mode, attach it to another machine that supports booting from your Mac OS X Server CD, install Mac OS X Server on the Mac Mini's internal drive, and finally update it to 10.3.8"
soi la, soi carré