I started an OSS project to enable me and my team to receive webhooks at a big co where Ngrok was banned and so was SSH. It works over an HTTP proxy using websockets. One of the requirements I had was for 1st class container support - so it could be run inside a K8s pod and support LoadBalancers for TCP traffic as well as HTTPS. The OSS project was very popular, but drew very little sponsorship. I then pivoted to a commercial license and got some more sign-ups, but not as many as I wanted - companies were happy to pay up front for a one year static license, but individuals and home users were not.

So I introduced a personal tier that was covered for commercial use - inspired by Jetbrains and added a monthly subscription option for it. Both of those actions helped increase usage and signups with personal users. Companies still tend to want to pay for a year.

Even though this is completely self-hosted software, developers seem to like paying for tools monthly. Some abuse this by cancelling the subscription in the months they don't expect to use a tunnel, or opening the software then cancelling the subscription and waiting until the process has to restart before re-subscribing. Not much I can do about this side of it.

If people are interested, the product is called inlets and is easy to find on the Internet. I also write about my OSS and independent business work each week in a subscription newsletter using GitHub Sponsors (another side project, if you like)

Books I could recommend: Monetizing innovation, Obviously Awesome, 1-Page Marketing Plan & Minimalist Entrepreneur. I'm not affiliated with any of these titles, but consider them core reading for indie devs and for side gigs.