I don't understand this per-developer licensing model. Not only is it completely non-enforceable but feels really out-dated and out of touch in the era of FOSS.Hasn't commercial software been licensed effectively per-user since forever? It used to be per-machine but these days with lots of developers using a desktop and a laptop I think it makes sense to say it's for one user at a time instead and avoid creating lots of silly infringements.
If you don't like anything resembling that form of licensing, perhaps you're projecting a preference for everything-should-be-free culture onto commercial development where someone has to pay the bills? Unfortunately, sometimes that just doesn't work.
Having a per-user or per-machine licence where the licence is not transferrable seems crazy to me, though. We consider such licensing conditions toxic, because all it takes is someone to leave or a hard drive to crash and you've lost your investment, so usually seeing that will end our interest immediately.
(For completeness: We will make a grudging exception for software that is essential to our business and can't be had any other legal way or replaced with any better alternative. However, you don't buy software like that with a quick web site download anyway, and if we get screwed on that kind of deal lawyers are involved. Obviously a charting library is nowhere near this level, though.)