I don't think Growl has a way or public API that would allow a remote server (Forge and/or your servers) to communicate directly to your local computer.
I could be wrong, but I believe only local services can trigger growl notifications.
Lastly, I'm not sure if you're on a Mac, but latest Max OS doesn't need Growl because it has it's own notification system (Does Growl still work on newer Mac OSes?)