Does it only work for logged in users?

I have this question too.

Would love the official answer.. but it seems the answer is yes:

https://github.com/13pixlar/gravity-forms-sticky-form/blob/master/sticky-form.php#L170-L175

// To save a reference to the entry we need the option key to be unique to both user and form
function sticky_getEntryOptionKeyForGF($form) {
    global $current_user;
    get_currentuserinfo();

Ah here-

Sorry, the user needs to be logged in for this to work. Maybe I will implement cookie functionality to enable users that are not logged in to save their forms.