Hi Cedric,
Before distributing the wgt file, please test it on your simulator.
you can install the wgt file using sdb commands
Example:
from command prompt
sdb push app.wgt /tmp/Application.wgt
sdb shell
wrt-installer -i /tmp/Application.wgt
If the widget is installed correctly on your emulator, then you can send the app.wgt file by mail to the testers. They can follow the same steps to install it.
Please try it.