YES, YES .. how many times I must repeat this before you will start just for test download some *ipws file?
Page like above contains only index of files on Apple site. If you will click on any *ipsw file it will start downloading from
http://appldnld.apple.com/:
$ date; wget
http://appldnld.apple.com/iOS6.1/091-3423.20130502.Tr3Lz/iPhone5,2_6.1.4_10B350_Restore.ipsw; md5sum iPhone5,2_6.1.4_10B350_Restore.ipsw
Mon Sep 23 13:00:53 BST 2013
--2013-09-23 13:00:53--
http://appldnld.apple.com/iOS6.1/091-3423.20130502.Tr3Lz/iPhone5,2_6.1.4_10B350_Restore.ipsw
Resolving appldnld.apple.com... 195.245.125.179, 195.245.125.137, 195.245.125.170
Connecting to appldnld.apple.com|195.245.125.179|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1037923480 (990M) [application/octet-stream]
Saving to: iPhone5,2_6.1.4_10B350_Restore.ipsw
100%[=====================================================================================================================================>] 1,037,923,480 24.4M/s in 40s
2013-09-23 13:01:33 (24.7 MB/s) - iPhone5,2_6.1.4_10B350_Restore.ipsw saved [1037923480/1037923480]
e4e8c5e724bd851bf14e018fc40f2d59 iPhone5,2_6.1.4_10B350_Restore.ipsw
You can download any historic firmware. You must only know full URL. As far as I know if you have developers account you can access to page with index of all *ipws files but download of any files as you see still is possible without any authentication or so.
Questions?