So, if you can learn for free, why make the others pay for a work that you made for free?
And be able to have a good login, ban system, funny mechanic plugins
And the amount of people can pay for a plugin is very low.
Because coding is free, yes, but the time, it's not. You can donate and gain access to this:
Unlike most of the free plugins, I constantly update my plugins if there's a bug, or If I think it can go better by adding new mechanics.
As a developer, I think that there're some plugins that can get better, and that's what I do, I rework from 0 old plugins ( or plugins that can be better ) and then, post it. It's not code stealing, because the rework it's from 0, the only thing I "steal" it's the plugin idea, wich should be free. An example would be "Commands", a private beta status plugin that will replace Essentials.