Looks like their DNS servers are responsive, but refuse to serve records:

    $ dig -t NS developer.apple.com
    [...]
    apple-lr.g.aaplimg.com.     14400   IN      NS      b.gslb.aaplimg.com.
    apple-lr.g.aaplimg.com.     14400   IN      NS      a.gslb.aaplimg.com.

    $ dig @a.gslb.aaplimg.com developer.apple.com
    [...]
    ;; ->>HEADER<<- opcode: QUERY, status: REFUSED
    ;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
    ;; WARNING: recursion requested but not available
    ;; WARNING: recursion requested but not available

Most likely a configuration mistake that'll be undone as soon as they figured out how to re-deploy their DNS servers while DNS is down.

Unlikely to be BGP shenanigans as some people on Twitter claim. My network has direct peerings to Apple's AS714.