En fait, ça fait déjà 3 jours que l'SDK en version bêta est dispo en téléchargement sur Steam tools, mais apparemment encore personne ne s'est relayée l'information et l'annonce officielle vient juste d'être postée :
"The Left 4 Dead Authoring Tools, also known as an SDK, is a set of software utilities that allow you to create your own levels, campaigns, common Infected, and other gameplay elements. They include versions of Source SDK tools that have been updated to work with the Left 4 Dead version of the Source Engine.
"The Left 4 Dead Authoring Tools are current in Open Beta Testing and are freely available on Steam to all owners of the PC version of Left 4 Dead.
What's included?
The package includes:
* Updated Hammer, the Source level editor
* Suite of command line compiling utilities, such as studiomdl and map compiling tools
* Updated Particle editor
* Updated Faceposer
* Example maps
* Example models: common Infected, a breakable prop, and explosives
* A set of example particle effects"
Source : http://forums.steampowered.com/forums/showthread.php?t=861395
Donc pour faire rager un peu plus nos z'amis xboxiens (taunt); n'hésitez pas à aller faire un tour dans l'onglet "outils" sur Steam et télécharger "Left 4 Dead Authoring Tools Beta" pour tester la bête. Et les devs en herbe, bah... au boulot !