Esther E.

This means no more sexy lonely women using the Contact Us form, lol

Wrong listener. There is a listener for invoice items as well.

I wasn't expecting this outcome. It's no secret it has been declining for years, so action was bound to be made. I like the Dev Directory, it's a very nicely made alternative and it gives more freedom to our Devs. Well done.

That's correct. I would suggest reaching out to the authors of the modifications to verify that their applications/plugins are compatible. 

In @Ehren we trust.

The new terms only begin once you opt in to the new terms.  
There's a certain amount of hysteria that these changes are being applied retroactively.  
If you don't accept or want the new terms and want to coast along on v4, then don't accept the new terms.
It's understandable that clients with your worldview will skip renewals, perhaps because of experiences in other forum ecosystems.  It would make sense that you are cautious about continuing to invest in an active license if, for example,your forum developer doesn't release any new features after years of no activity. If you truly and authentically evaluate IPS on its own merits by looking at the Release Notes and the Company blog, however, you'll find a development and release cycle that is robust, monthly, and feature rich.  
The terms by IPS seem more stringent in light of other ecosystems.  I invite you to evaluate IPS on its own merits, instead of imposing the fears from other vendors.

Honestly, the process was fantastic, and the discussions were numerous. While IPS does want the CIC product to be their primary product, they see the value in being the best self-hosted product on the market as well.
But as they've said for a while, the self-hosted market is changing.  Sites that are "just forums" are not likely to survive long going forward, which is a position I've held for years back when I added IP.Content/Pages as the article management system on my site.  As such, it doesn't make sense to keep the apps as individual products anymore and instead sell the suite as a whole.  It allows IPS to integrate the apps even tighter. 
In my view, site owners who run "just a forum" need to sit back and reflect on where the world is today and if such a site makes sense to continue self-host, or just migrate it to Reddit instead. If you are a "just forums" site owner, I would encourage you to look at this change as a chance to grow in new ways with the new apps that you didn't have access to before.  The only limit is your imagination.
IPS published several drafts of the upgrade language to us in the group and we all took turns making suggestions and modifying the language.  While IPS certainly set the guidelines, it was a very collaborative effort between IPS and those of us in the customer focus group. I think every person in the focus group submitted a modification suggestion to IPS and IPS was very receptive towards them. 
With regard to how the licensing changes work, especially regarding renewals, it's clear that in order to make sure the self-hosted product is a viable, ongoing product, people who use the software need to chip in. The pool of self-hosted customers has shrunk dramatically over the last years. Making the renewals and catch up fees mandatory was the only way to do that in a fair manner but IPS counters that with lower renewal fees for any site with 2 or more apps.
My relationship with IPS over the last 20-ish years has been strained from time to time, but I have to say that this has been a fantastic experience for me personally.

Honestly I like this. I do appreciate the self hosted option and I think IPS deserves to be compensated for continuing to provide the classic version. 
 
This provides a creative solution to an ongoing problem and allows a path forward for the self hosted version. 
 
This should allow both classic and cloud versions to co-exist for years to come! 
 
Kudos to whomever developed this solution! Thank you for not giving up on the self hosted version!!! 

What you're asking for is not just "laborious", as you described, but pretty much near impossible. We'd have to list literally every single element of every array (in the example you gave there are probably close to 50 possibilities alone) in every template. Anyone even slightly familiar with the code base would have no issue figuring that out, so this would be a very big effort targeting a very small number of people... and maintaining it would be a nightmare.