We have made one premium and two free WordPress plugins. There are about 3600+ active installs of free plugins (hosted on WordPress.org plugin repository). And premium plugin has less than one hundred active installs. We do not have enough time to support and expand this business, so we decided to sell it. A project website has a fully working support forum system, licencing engine, purchase engine. Also, all plugins have documentation.
Get in touch with the owner to discuss the tech stack, market size, or just make an offer!