As often, it is the small developers who pay the fees, especially when they often have to modify their programs and the difficulty that they have from their status, to obtain a certificate.
But I also understand that antivirus do this, otherwise it is the door open to the spread of malicious software
@eh.ouais (et oui quoi 
) : I do not know the notoriety, the circle (private, public) of the users nor the utility of your tool but can not you prove, to pass the trust/fair to your customers / users?
I am an user of a healthy tool proposed by a “small” developer.
The tool is also often modified (twice a month) and avast shows me the same message of mistrust, but I authorize it with each change without having to wait for the response of the avast verification.
Of course, I do so knowingly and I do not know if in your case your clients can do this. ???
