astro1138 parent
There is no source code either for the WiFi stuff in the ESP8266.
That has yet to be an issue in my experience.
It's been an issue for me. I wanted to make a battery-powered sensor that would only enable the wifi hardware when the sensor had changed (to maximise battery life) - but the closed-source firmware means that's not possible.
Also, some of the SSL support is in the closed-source firmware, and it's incompatible with Mozilla's 'Modern Compatibility' ciphersuite list.
I used the ESP8266 anyway - it's not ideal, but for my application it was the best thing available. There's room for improvement, though.