What happens when a program gets removed from the Software-Center?

If Canonical removes a program from the repositories of the Ubuntu Software-Center, what exactly happens to my installation?

I like using the Software-Center to easily find and install programs on Ubuntu and to manage updates so that the software is always on the latest version. As an example, I'm using the program MediaInfo (for no particular reason). MediaInfo changed their licensing from LGPL to FreeBSD recently: While it is still FOSS, it may be possible that the program (or any other program out of the Software-Center) gets bought by a company that applies a proprietary license or adds other functionality that does not agree with the terms of the Ubuntu software repositories made available to the users in the Software-Center.

In this case, it will likely be removed from the Software-Center, if I understand it correctly. What will happen to the program on my computer, if I already have installed it at that point?

Will it automatically be removed from my system? Will it just not be updated to the next version? Will the last appropriate version still remain available in the Software-Center? And will I receive some kind of notification about any of this?

While it is still FOSS, it may be possible that the program (or any other program out of the Software-Center) gets bought by a company that applies a proprietary license or adds other functionality that does not agree with the terms of the Ubuntu software repositories made available to the users in the Software-Center.

Not being FOSS or having a proprietary license has never been an issue for Canonical (see the restricted and multiverse repositories).

If something can't stay in the repositories anymore for other reasons:

What will happen to the program on my computer, if I already have installed it at that point?

Nothing. It will sit there peacefully.

Will it automatically be removed from my system?

No.

Will it just not be updated to the next version?

Yes.

Will the last appropriate version still remain available in the Software-Center?

It depends on the reasons behind the removal. E.g. if a package is harmful, indeed it will be removed.

And will I receive some kind of notification about any of this?

No.

You can however check if a package is not in the repositories at any time by running apt-cache policy <package>;

A package that has no available version in the repositories won't show a version available from the repositories as a candidate for the installation.

No installed package will be removed, if Canonical removes a package from the repositories. The same for a PPA or any other repositories. The only thing that has happened, you will no longer receive updates.

If the package should be included in the repositories again, then you will again receive updates. But you will not be explicit informed about the returning.