yes, prodesigntools.com links directly to adobe's servers. i can't tell you why adobe doesn't offer non-current software links on its own website but links for cs3, cs4, cs5 and cs5.5 products (and more) are all on prodesigntool.com. all those links point to adobe.com servers.
per john waller, who's more knowledgeable in this area than me, i was wrong: the ps cs5 offered at prodesigntools is the extended version and will activate to the extended version with your serial number.
be sure to follow all 7 steps. in particular, meticulously follow steps 1,2 and 3 at http://prodesigntools.com/all-adobe-cs5-direct-download-links.html
p.s. thank you to john waller for correcting my misinformation.