If you use your browser and not Galaxy, click on the game in your account, and then More, and then Serial Keys.
See attached pic.

So it's a year later after this post, and with the recent changed to GOG Galaxy 2.0 & the browser, where would one find said cd keys now days?

I cannot for the life of me find this "MORE" button.

Any help would be greatly appreciated.

In the browser, hover your mouse over your username and click games.
Find NWN2 in your library and hover your mouse over the bottom right hand corner, a down arrow will appear.
Click on "VIEW DOWNLOADS" and you will see the screenshot in the post above.