This sounds like such a trivial thing to do but it wasn't the most logical.
Alright, you'll need a tuple that contains the True/False value and labels and then a ChoiceField which uses it.
class CustomForm(forms.Form):
BOOLEAN_CHOICES = (('1', 'True label'), ('0', 'False label'))
# Filtering fields
is_true = forms.ChoiceField(choices = BOOLEAN_CHOICES, widget = forms.RadioSelect)
Oh what? We're done!