Hi,
As you are using the development version, the fact is that the headless plugin (msi.gama.headless) comes with a launcher (2 in facts).
You could try to run the launcher: msi.gama.headless.id4.launch (that should execute the same models than the examples provided on the website).
If I am not wrong, but I am not sure on this point.
The scripts are only here to be packaged in the GAMA release versions; I do not think they can be used to run the headless mode.
The big BUT to this, is that on my version of the dev version of GAMA, the launchers do not work ...
We have to investigate whether this an issue or a misuse from my side.
Sorry for this unsatisfying answer.
Cheers
Benoit