I thought'd I might contribute a perspective from a user/site builder/low level developer.
tl:dr this is about plugins, not core development Apologies if deemed a thread jack, as references to plugins came up in the discussion. Feel free to split off.
Some background: my experience with WordPress and Drupal stretch back more than a decade. I almost excessively work on not-for-profit community sites (I never touch, or fork, core).
I am building a couple Discourse sites (with and without WordPress integration at the moment (alongside a couple other WordPress and Drupal sites). With WordPress, the abundance of low quality paid plugins — and it is time consuming/can be very difficult to determine their usefulness and quality — is a challenge (I mostly write my own functions where I can). That so many of the plugins (even themes) are poor hacks is similarly an issue (very poor usability outcomes).
Drupal, which has a much steeper learning curve, does have plugins that are similar of lower quality, thought these are quickly displaced by other through a community of developers. Closed source — like the WordPress marketplace fosters — actively prevents this to a substantial level. This is not to say Drupal's approach to contributed models is without issue.
My experience with Discourse counts in months. In looking at the architecture of a community site, funding ongoing expenses came up in discussions. I searched for options and came across the PayPal plugins built by @dmitry_fedyuk — initially considering they might be an option. However the closed approach inhibits an ability to assess their quality without first paying for them. It also brought to mind the 'plugin wasteland' of WordPress and how painful it is.
I see such a model as fundamentally against what I understand/understood Discourse to be, and why I have looked at it as a (potential) solution for some community groups.
In short, crowd-contributing to/funding plugins, rather than a licensing model, is more what I was expecting-hoping for based on past experiences — and is what I thought was in the spirit of how discourse was envisaged and developed.