Pomodoro is an interesting technique, and it's something I'd quite like to try.
But I'm struggling with a couple of things here;
- Why use github when it's closed source? Github users tend to expect to be able to see the code and use it freely. (With larger projects, some features may be paywalled)
- What are you offering to justify it being paid? Especially when there are a lot of free pomodoro timers out there (Two websites - https://www.freepomodorotimer.com/ https://www.tomatotimers.com/ and desktop tools)
I'm a developer (well, sysadmin,but I write a lot of software both for work and as a hobby). I don't see your method as viable, but perhaps I'm wrong. I wouldn't pay for such a tool when there are free alternatives. I can't see how much work you've put into yours, but this sounds like something simple that wouldn't take long to write, vibe or not. I'm also a big fan of FOSS, both as a user and an author.
So basically, what's special enough for it not to be FOSS?