I don't think I'll share the details in the future, but it's an experiment for sure. I've seen success by selling one-off licenses of Monokai Pro for Sublime Text and VSCode, where I used the same mechanism: everything is free to use, except you get a pop-up message every now and then. People that want to get rid of the popup or offer support can then opt to pay for a license.

I understand it's uncommon practice to ask a fee for a set of colors. The reality is that making a theme and keeping it up to date is not trivial. A color theme, custom icon graphics and IDE config, along with code to glue it all together when you switch filters does take some time to make. And the codebase is different for each editor (Sublime: Python, VSCode: JavaScript, Jetbrains: Kotlin). I think it's not unfair to ask for a small fee for this work.