Hello, I looked at my Sky router a while ago and got bord, attached is the Serial interface pinout I found.
You can connect to it (standard console), to see the "other software" running on the router.
I think the JTAG pins are on the other side, where the connections are too small (for me) to connect to.
I can't quite remember - but the line username/password is stored in one of the top partitions, so you can use them on a different router.