Honestly, I'd say go for it, open-source it. Like you said, a successful app's more than just changing icons and the like!
One tip - maybe you could think about constructing a tutorial of sorts around your app's codebase? Something like this: https://mackenziechild.me/12-in-12/
One tip - maybe you could think about constructing a tutorial of sorts around your app's codebase? Something like this: https://mackenziechild.me/12-in-12/