@Eliot:

Thanks a lot, we're making progress : it's part of stdlib and it launches the engine. :) I was searching for Amiga-specific functions when the standard one was available!

The only problem now is that, if the GUI is run from the shell it displays the engine output in it, or if it is run from the wb, even worse, it opens it's own output window. I'll have to find a way to redirect input and output I guess.