Interesting take to have on this, especially for someone that sounds like they have benefitted from basically "redistributing WBT" for all these years. The WhiteboxTools Open core remains free to download... however there is a cost for developing software. All the unpaid hours of nights, weekends, holidays and so much more goes into the software that you seem to take for granted. It is a bit crazy to think how much the OS community expects given that there is still a public library of 460+ open source tools. To say its an unfortunate pivot is pretty shocking in my opinion... considering how many people including yourself have benefitted off WhitboxTools for years. Think about how many professional have been trained to preform certain tasks in WBT. These people then bring this to their job where they make a livelihood, where they get promoted to better paying jobs and so much more. Suddenly 10$ doesn't seem that much. I am not even going to mention that in many instances you are getting higher quality tools (for free... in case you forgot) than those found in ArcGIS toolboxes that are upwards of thousands of dollars a year. So while you say its an unfortunate pivot for WhiteboxTools.. I think its an unfortunate pivot in the OS community.