Does GoG employ PortingKit dot com or PortingTeam dot com? Or what other magic for wrapping windoze games to OSX?

Nope, but they do use Wineskin (self-contained Wine apps) like what is available through PortingKit, and a GOG-specific version of Boxer for DOS games.

GOG uses Wineskin, which is one of several user-friendly distributions of WINE for Mac OS X. Much like DOSBox, Wineskin is F/OSS software. I don't know for certain, but I'm sure that doh123, the person primarily behind Wineskin, has had some paid involvement with GOG. It may be similar to Alun Bestor and his involvement with GOG's use of Boxer to power their Mac-compatible DOSBox games.

PortingKit is primarily driven by PaulTheTall, in collaboration with doh123 and several others. Under the hood it's almost identical to how Wineskin works, but instead of Wineskin Winery, PortingKit has a special custom front-end that's intended to automate and streamline the installation process, in addition to being a portal for PaulTheTall's own forums.

In short, GOG's own WINE-based ports and PortingKit (in addition to Wineskin) both share the same underlying technological implementation of WINE on Mac OS X. If you want a (largely) no-muss, no fuss, one-click installer for your (supported) WINE games, PortingKit is excellent. If you want more fine-grained control over your WINE-based games, Wineskin is what you want.

In addition to this, there's of course CrossOver, in addition to PlayOnMac, the OS X version of PlayOnLinux.

Is this somehow not a spam account?

I've been wondering about this all day, waiting for someone else to suggest it. :P