I would probably not go so far as requiring such a signing process in
the license. But it would put an enormous public pressure on web
services. If they can prove for a small sum that they run only free
software, why would they not do so?
Because there will be hardly any public pressure. We all say that people
should use free software. Even though there are free pdf readers available,
the only publicly well known one is acrobat reader (which is I believe
renamed, but anyway). Free software isn't a big issue for most people.
Because they value their privacy!? Something like the way you say you
value your freedom. "If it is for free, and technologically better,
why don't you take it?"
This is not about things for customers, it's about things for service
providers. I know in some cases the line between them is blurry.
Say I provide a service to people who don't know you, for example web
hosting. Assume that you want to use my service for your company, and that
you want to put some internal secret company data in a protected section of
your site. You will want to make sure that unauthorized people cannot access
that data, and that includes me. So if I don't prove to you that I am unable
to access it, you will not do business with me, or at least not put that data
on it. Then we both lose. In this case, the fact that my customers know I
only use trusted free software is more important than the fact that I always
have the newest technologically better system. Bug fixes must of course be
installed, but I'm sure that can be done as long as they are signed.
However, if we are friends and I happen to have a computer permanently on the
internet, while you don't, I can also host your website. In that case, I may
just install every new feature that is released, or that I wrote myself. No
need to do any verification in that case.