I've only spent a few minutes researching this, but it seems Apple use a semi-proprietary netboot for their network boot option (hold down N key). It is well supported by Apple's NetBoot and NetInstall services on the Mac OS server. I've seen a couple of howtos on making Linux with netatalk and patched dhcp do the full netboot trick.

Has there been anyone able to boot the macbook client from Linux server for purposes of using udpcast?

--Donald Teed