I don't have a post about it, but the equation is pretty simple: good cross-platform software + good documentation + responsive development = good product. The trick is to write good software -- the license doesn't matter so much. But, making it free/libre is competitively advantageous, all else considered. Some customers have told me they would not have considered paying for a proprietary option.
My project is called reMarkable Connection Utility (RCU), and it makes about $2.1k MRR, selling ~200 copies/month. Some months are worse, some are better.
I've never purchased any advertisement. Its users advocate for it through online forums. That genuine attestation, to its quality and also to me as a person/programmer, helps it sell. That its users, too, are free to share their copy with friends helps people encounter the program who otherwise would not have purchased forthright.
I sell it from my personal website with links to PayPal and Stripe. The return URL is its download page. No JavaScript anywhere. I provide the entire Git history of the project, as well as binaries for all major distros of GNU/Linux, FreeBSD, Windows, and macOS. I also provide two mailing lists -- one for all customers to be informed of updates, and another for customers to talk with each other, see my latest code patches, and talk about its general development and the reMarkable tablet.
There's nothing to stop any of your paying customers from setting up their own site and giving away (or selling for cheaper) copies of RCU, right? I'm guessing you understand that and figure the downside risk is low--small numbers, low stakes, consumer focused, good vibes?
That's right, and they have, but I still earn enough income to develop and maintain the program. Free redistribution does not hurt my sales because people who would have paid for the program do, and those who wouldn't can end up trying it, a fraction of whom go on to become customers because they want updates and support from the most-trusted source (me).
You'll see a very similar thing elsewhere: illicit file sharing increases box office revenue and increases album sales.
Anyone who wants a no-fee copy of RCU can find it many places by searching. If someone ever extends my program with a cool new feature, their version must be released as AGPLv3+, and that means I can re-incorporate their improvements into my own offering. The market dynamics of free/libre software are such that since I have the reputation, the first-mover advantage, and the top search engine rankings, then anyone looking to compete needs to do so on quality of features -- which I have the license to copy, just as they copied from me. Anyone who wants to compete with me needs to compete with all that.
Anyone who shares my program ends up promoting it in the best way possible, by talking about it and telling others it's good and worth using.
