The SourceMod, a server modification that has been in development since late 2004, has been updated to version 1.2 with support for Left 4 Dead and Dark Messiah of Might and Magic:

"SourceMod is server modification for any game that runs on the Half-Life 2 engine. It is a powerful, highly optimized platform for scripting plugins and handling server administration. The default package comes with a base set of plugins, but there are over 450 plugins in the community."

That means that over two years after its release, Dark Messiah finally gets modding support... the unofficial way. You may remember that the SDK promised by Ubisoft was never released, despite the work that has been done by Arkana. Thanks to Mana who brought me the good news.