At no time did Valve grant permission nor discuss these advertisements with Engage. As such, this is now a legal matter. Advertising or any other commercial use of our games requires our written permission.
The idea of in-game advertising may be no big concern to some, or treachery to others, but it is a viable method for online gaming to find other revenue, especially if the online half of the game is free. However, it of course must be done properly The exact extent of what, if anything, Engage did wrong here isn't completely clear, but it will be very interesting to follow as it unfolds.