There is a difference between a commercial effort and calling something commercial software, which often (usually?) refers to licensed per use (often per installed system) software. Open source must be freely redistributable, which means it can't have a per use license.

I think the main issue is the name. If a project is made more commercial or proprietary than it was before, please change the name (or additionally use a different name for the commercial/proprietary part, which seems to be common practice even when starting a project as partly open source). A clean break between different maintainers (particularly when a mostly single person effort) is a good reason to change the name too. Naming things is hard and it doesn't necessarily need to be all that different a name just something to reflect the change.