Revenue sharing for wordpress.com premium themes?

Hi dear WordPress people

Assume that a designer creates a theme that is later published on WordPress.com as a premium theme (that is, people need to pay to use it). Then, does the designer make some money on this? That is, is there some revenue sharing between Automattic and the designer?

What about premium plugins? (But perhaps there aren’t any premium *plugins* available for a wordpress.com website? Only *themes*?)

(As far as I’ve understood, there need not be such an arrangement, since themes are GPL compatible (well the PHP code at least), and anyone who has the theme source code could modify and redistribute/resell the theme, and they would not have to pay the original theme designers.)

((Any case (both with and without revenue sharing) would be fine with me, perhaps I should mention — because when I asked a somewhat similar question elsewhere, someone seemed somewhat upset. However I suppose both cases would be in the spirit of the GPL
— that you’re free to build upon the work of others and redistribute/resell.))

Kind regards, KajMagnus