These are the sources from Adam Agnew and Adam Sulmicki that let you boot OpenBSD, Windows, etc.
Is there any HOWTO on this ??
Just read throughout the files provied with ADLO. the "INSTALL" file is a fairly good start, README would be next. But you probably want to go over all of them.
Then let us know what/if needs to be changed. I have been pretty much living and breathing ADLO for last few months so something I think may be obvious may actually be not.
This or either way, the target audience for ADLO is experienced LinuxBIOS "users".