The activiti inside alfresco is rigged with special handling for tasks, jobs, authentication, scripts, …
So using it from activiti-explorer will very likely give a lot of exceptions or potentially mess up worklfows in alfresco, as the explorer-app is unaware of those special hooks.
AFAIK, that's a NO-GO. If you want explorer-like-funtionality, you should check out the enterprise-version of Alfresco, which has an explorer tailored for alfresco built-in, wired in to use the right engine and context.
