I didn't expect to see this. Wow. AGPL works: developer has some say now. @seanharrison thank you for sharing.
Let's split from this a second observation that developers are not always good at negotiating. Lawyers/brockers have this excercise more often: side A wants X, side B wants Y, where is a middle ground for a deal to make happen.
By the way, deal is when both sides give in.
Obviously, there are no articulated and promoted patterns for an agreement here. It would be nice to have a few. We should ask FSF and likes to compile and articulate patterns so that devs on both sides have something to start with.
Nevertheless, let's hack out suggestions, like we hack out code in absence of any hints. Let's be pro-active. It won't hurt, i.e. don't comment that we are going out of scope, since actual application of licensing regime is functionally within the scope of this topic.
How about suggesting that pay is $x, while you are small, going up to $y, when you grow? Specify what small and later are. This way you tell developer that you are real, and you have a similar pain.
Also add a provision that if buying party gives away software to a bigger related company, related company's use of software matters.
Also, agreement should talk about acquisition of buying side.
I'll be at LibrePlanet 2020, and I'll personally bug non-tech guys to write some agreement patterns, semi-blessed, mostly explained for devs' consumption.