Interestingly Apple does use NetBSD on their Airport Extreme and lock it.
Even the older iPods modified PixoOS is encrypted.
In case of a router like the Airport Extreme, if the built-in firmware was a pile of crap, I'd be pissed, but the Airport Extreme is the single best router I have ever used. Never had a compatibility issue with it, the utility used to configure it is 1000x better than any web form I've ever used, and it has damn good throughput over wifi (I've hit 40 Mbit/s over wifi with mine, not even 5 Ghz wireless, just regular ol' 2.4 Ghz).
As far as the modified PixoOS on the iPod Classic. It works as advertised, damn near flawlessly. I've played around with iPod Linux, and Rockbox, and while they're both great replacement firmwares (or at least iPodLinux -WAS- until the project fell apart [for those in the know about it, I'm still waiting for hotdog goddamnit]), they're just not practical on an iPod (although Rockbox may have gotten better, haven't used it in a while, and I don't have a decent screen for the iPod Classic I built, so I don't really wanna mess with it just yet.
tl;dr Airport Extreme and PixoOS are encrypted and locked, but on those devices, it's probably one of the few cases where it's for the better.