So, I'm playing along, doing pretty well, steamrolling all my enemies, researching at superspeed. So I get up to Corporation, and build some Corporate Branches, thinking that Franchises sound pretty neat; my enemies don't have lawyers yet so I can just rip them off with impunity, right?

Well, after dozens of franchises, in BIG cities no less, I have yet to see ANY decrease in my unit upkeep costs. My enemies are totally pissed at me, and I have nothing to show for it!

My questions are:

1. Are franchises bugged in the current, standard GOG download?
2. Do I need to install Apolypton to get franchises to work?
3. Are franchises, in fact, working, but I haven't figured out the interface enough yet to see it?
4. Is there something else I have to do to get franchises to work? Do I need to be a Corp. Republic? Do my opponents need to have Corporation/Legal Code? Do I have to have an embassy in the city?

You should get a production bonus, possibly noticeable by a public works increase.

So far as corporate branches go, i only use them on AI that annoy me.

And don't worry too much about diplomacy, as with most games that have it, it is fairly pointless.

Don´t know if you are still interrested in an answer:

But if you are so big, the ´income´ of the franchise isn´t really a big help for you.

If you check manually via the military advisor your upkeep cost (production) versus IIRC via the diplomatic advisor the income per city, you find that it is not more than a drop in the bucket.

For example, your overall production is like 5000, your military costs 500, resulting in 10% production loss.
Now you franchise the shit out of your far weaker enemy and you get like 20 production out of it for 10 cities, makes 200 production, which is added to your OVERALL production, so you will have a production of 5200, meaning your percentage upkeep is now 9.6 %, or still 10% ingame :P

Don´t forget, you only get a portion of their production.

This is kind of only worthwhile, when you are struggeling, like in the beginning with slaves. Man those really help you in the beginning........