Gravity Perks Limit Checkboxes AddOn
This plugin allows you to limit how many checkboxes of a Checkbox field may be selected at any given time. It supports specifying a minimum and maximum limit per checkbox field and also allows you to span one field’s limits across multiple fields!
Limit how many checkboxes can be checked.
Set how many choices users can pick from a single Checkbox field.
Set minimum and maximum limits per checkbox field.
Users must pick at least x, but no more than y.
Span limits across fields.
Share limits across multiple fields in a single form.