The JSF Guestbook uses the PageContextAdapter class, which no longer exists. This is referred to in our docs, and breaks the portlet in the learning path. References in the docs are made in Adding Action to Your Managed Beans and Defining Portlet Actions and Permissions.
Neil explained that one of the goals for using this originally in the learning path code was to get a Liferay permissions URL. We developed a more JSF-ish way of doing it here:
http://www.liferayfaces.org/web/guest/portal-showcase/-/portal-tag/portal/permissionsurl/general. This is one of the reasons why PageContextAdapter went away.
We need to update the learning path code and documentation to reflect this change.