Does the WiFi alliance protect the protocol documentation?
The Wi-Fi Alliance is a trademark management corporation. None certified products are produced all the time. The only thing the Wi-Fi Alliance does is license the name "Wi-Fi" and certifies for inter-optibility with the official 802.11 specs.

802.11b/g/n is fairly open, and the specs are managed by the IEEE, not the Wi-Fi Alliance. None certified, none patent paying wi-fi compatible products are produced all the time.

But you would pretty much need decades of experience and a ton of free time or money to produce a consumer capable wifi chip, from scratch, as a single engineer.