[Solved]-Django form and i18n

You should use ugettext_lazy():

from django.utils.translation import ugettext_lazy

# ... 
  agreed_tos = forms.BooleanField(label=ugettext_lazy('I agree to the terms of service and to the privacy policy.'))

Model and form attributes are initialized when your Django application starts. If you use ugettext(), the translation will be set once at initialization and never change. ugettext_lazy() solves this problem by translating the string when its value is accessed rather than when the function is called.