No problem with the 4.X version of the add-on being charged for separately.
Problem with things continuing to break on 4.X updates... I get that the finger can be pointed in both directions, IPS devs & add-on devs, but finger pointing isn't helping all that much... right now there's a 4.1.19 update marked as security-related that breaks this add-on, leaving two options:
Update, be secure, and break the add-on.
Wait, be less secure, and hope the add-on is fixed or that IPS patches to 4.1.19.1
Both options are poo. Whatever can be done to prevent poo options being forced on us is an improvement.