I came across meteobridge today, a weather datalogging software package that sits atop OpenWrt on tiny TP-Link hardware. They sell the hardware too, if you want, but they also tell you how to set up your own hardware and then add the meteobridge package (paid, closed-source) as an overlay.
Structurally it’s very similar to how MiOS is layered on top of OpenWrt.
Perhaps there is something to be learned from their very good Open Source Obligations page.