I have learned from this article http://technet.microsoft.com/en-us/library/ee428324.aspx that "the default setting for associating a workflow is to allow users with Edit Item permissions to manually start a workflow".
Is it possible to allow users to manually start a workflow on a list with Read-Only permissions? The workflow itself does not update anything from its associated list, rather it creates a new item in another list (with Edit Item permissions) based on the information on the items within this list.