Welcome to the Q&A Forum

Don't be surprised by Google's inability to penalise obvious breaches to its TOS. So many sites slip under the radar. Case in point, after looking through the top backlinks in OSE and MajesticSEO after you sent me the URL (thank you very much by the way), I think it's clear how they've done it. There is an absolute ton of links coming from high PA/DA .jp and other Japanese domains pointing to the site. Furthermore, it looks as though the site may have been hacked at some point, because there's a load of high PA/DA viagra links as well - most of which look deleted now. Both of these sort of links, while without question unnatural, would pass page and domain authority to the site.  As for why it hasn't been penalised yet? Well, you may be able to see that the linking anchor text to the site is 95% raw URLs (as in: http://www.example.com/).  This means that they would not have triggered any Penguine threshold for over optimised anchor text, leaving it to the algorithm to work out the spam another way, and perhaps it will only be penalised when reviewed manually. It's an absolute ton of raw URL links coming from high PA/DA, but completely suspicious and irrelevant, websites that has caused the site's authority to sky rocket. Hope this helps clarify a few things.