The username/password parameters of SyncBuildEx only apply to other processes started by the build. The identity of the build thread itself (and actions like Copy Files, Run Script, etc., which execute on that thread) when called from WebLauncher depends on the context of the page/code invoking the VBP object model.
http://www.visualbuild.com/Manual/syncbuildexmethod.htm
http://www.visualbuild.com/Manual/weblaunchersample.htm
http://www.kinook.com/Forum/showthre...?threadid=2846
http://www.kinook.com/Forum/showthread.php?threadid=937
http://www.kinook.com/Forum/showthre...?threadid=1755