second and third arguments are optional. environment default argument is 1. So the GTK_MODULES and GNOME_ACCESSIBILITY will be set and added to the enivronment variable. Currently the second argument is applicable only when the test is run in local environment.
Refer: http://webcvs.freedesktop.org/ldtp/ldtp/python/ldtputils.py
from ldtputils import *
launchapp ('file-roller')
launchapp ('gaim', 1) # Invoke the application after setting environment variables
launchapp ('file-roller' '/home/ldtp/test.tar.gz', 0) # Invoke the application with optional command line argument