Huh. Since when did Spiderweb start outsourcing its games? Reflexive Arcade just added it to its game list, and it says it was developed by Oberon Media. They even used the screenshots from the Avernum page.
They have a 14.22MB trial and you can buy the full version for $19.95. Unless you, the management, are getting some sort of royalties from this, I suggest you take it up with them.
here's the link: http://www.reflexive.com/AvernumIV.html
heh. registered for the sole purpose of telling you this...