Earlier quoted context omitted.
I don't see where it is not ethical. At any point you can decide to pursue or stop maintaining the code and anyone can decide to fork and take over. It is just naive to think you will always find fun in working on it or pretend you might make a living out of it unless you have a strong business plan.
In the case of industrial control, database tech, and other high cost fields it would be dubious to pitch an open source product and then abandon it. Getting a high adoption OSS project takes more than putting a repo on GitHub. In some cases like this one, it’s possible that the underlying cost of these activities is much closer to the licensed proprietary software than the OSS variant (aka free)
Why? Open source projects are released with "NO WARRANTY", which includes the possibility of dropping maintenance at any time. If you want continued support you either fork the project and DIY, or pay someone to support you.