The Project Schedule list has been deprecated and withdrawn from the BrightWork user interface. The list will continue to function in existing Project Schedule based projects and templates, but it will not be possible to add the list (even via the list template gallery) to a new BrightWork template.
We are working with existing customers and encouraging a migration to Microsoft Project Professional 2013 for task scheduling. Microsoft Project Professional 2013 Sync is what we at BrightWork believe is the best schedule solution with SharePoint. We will continue to support existing customers using the Project Schedule list on the SharePoint 2013 platform, however we cannot guarantee 100% reliability on the on the SharePoint 2013 platform.