I will sing the praises of git and vim, but I didn't pay any money for them. He says extract a commitment, not necessarily a monetary commitment; I read half a book before I started using git, and vim took a lot of practice. So you could use more specialized terminology or something like that. git and vim are both very well-spoken of, and I probably wouldn't have bothered to learn them if they weren't. But I also don't bother to spend money on things that don't have a good reputation, if I haven't had experience with them already. So, either way, requiring a commitment from the user turns away a lot of them. (I've never read your website)

I wonder if a donate button at the end of each article, tied with a question along the lines of "How valuable was the article you just read?", would be effective. (You could even set it up so that you can track the amount donated by article, and use that to guide future research- I'm not sure how effective that would be, since that depends on how many alternatives you have to pick from in considering new research topics.)