430EX - what isn't in the manual

Just acquired a used 430EX, and have been reading manuals and tutorials and am now confused. Both say the 430EX cannot be used as a master. I know what master and slave are, but is this referring to only Canon speedlights? My 20D can turn off the focus assist, and the 430 will work in manual. So why can't this be used with another brand of flash that has a slave function and is triggered by the light itself?
I have a Quantaray which is similar to the Sigma DG Super. I have fired that as a slave using the Sigma DG ST, and a Sunpak 50. Both the Sigma and the Sunpak are Ettl-II compatible. If someone can explain this - I'd appreciate it.
Thanks,
Carpetshark

All references to "master" and "slave" in the EX flash manuals relate to the Canon wireless system which uses intelligent optical commands to control slave function and output as well as to trigger them.

If all you want to do is to optically trigger "dumb" optical slaves, any flash can do that, including the 430EX. Of course, in this mode, the flashes will need to work in manual mode (E-TTL mode cannot be used).

Thank you. I expected that type of tutorial from Canon - but I guess a lot of the independent tutorials also quoted the Canon ones. No one seemed to make a reference to a kludged system. I suppose I'm not the only one to kludge, either. <br>
Carpetshark