TP-Link agrees to allow third-party firmware in FCC settlement

All they are restricting is the power you can transmit at. That could literally just be a burned-in dB value or a set resistance on a circuit. There's no need to configure that as, by law, tweaking it beyond normal parameters is illegal anyway. It's like saying that a TV card isn't "open-source" because you can't tune it down to receive at 0.5MHz.

There's also nothing saying the radio power can't be adjusted, just that the MAXIMUM must be respected. As I say, if they do this by putting a certain resistance into a circuit, that still lets open-source firmware dial the transmission down, like managed Wifi systems do, to increase global throughput.

Open-source is not about "you need to be able to do control every possible theoretical function of the system". It's about "if proprietary firmware can do it, so should we be able to". And the maximum transmission level is not something that proprietary or open-source firmware should be able to exceed, because of the laws around this.

Historically, the maximum transmission level wasn't even implemented. Now it will be implemented in hardware or at least outside the scope of ANY firmware. That means proprietary and open-source firmware are back on a level peg again.

Sure, it means you can't exceed the maximum transmission level, but control of the device for any legal purpose isn't hindered at all.

Sometimes OS-evangelism goes too far. Even if you were to make an OS router yourself, you wouldn't be able to get it FCC certified without literally removing the capability for users to tweak the maximum transmission power level. So restricting that isn't about removing your software freedoms as much as making devices that are legal to use, buy and sell.