Activision is the publisher, not the developer. The developer is Cauldron.  

 Offical Site? 

What confirmation is there that the offical site is offical and not just a fan site with the logo on it?  

I checked the page mercenarieswanted.com and it seems it was registered to an advertising company called "Gabriel deGrood Bendt" while a search of doom3.com or callofduty.com shows are registered to Activision(obviously).

you can check by yourself by going to a domain information website like: checkdomain.com

Note that if you visit their website http://www.always-thinking.com/ and click on the 'our work' tab you'll find that Activision is a client.
The advertising company is located in the same City / State as ActivisionValue (Although that may be purely coincidence).
Two games that this company did advertising work for were both published by Activision Value. 'Pimp My Ride' and 'World Series of Poker'.

Mystery solved I think.