All meshtastic code is GPL, the name "meshtastic" is owned by the company that developed it. You can use any of the code, you can't use their name outside their rules. This is absolutely no different than, say, Firefox. The trademark policy is very permissable and you don't even need their permission to use the name on a commercial product.

I think it's totally sensible for the organization to want to have some level of control over what gets their label on it -- the Wi-Fi people wouldn't be very happy about someone slapping their logo all over a bunch of completely incompatible hardware.

Nitpicking, but IIRC, Wi-Fi was born largely as a marketing effort rather than a technical one. Interoperability was an afterthought.