Another way to understand Morea is by contrasting it with other tools used by educators to create course content.
GitBook, like Morea, creates educational websites using Markdown and Git. If you want to write a textbook, GitBook is a better choice. Morea is preferred when you want to create a course curriculum from a variety of sources including your own and/or other sources, and when you want to make learning objectives and assessments explicit.
Learning Management Systems
Blackboard is one instance of an "enterprise learning management system (LMS)" that provides comprehensive support for all aspects of course management: content management, testing, grading, etc. (Others include eFront, Moodle, Ilias, Dokeos, Sakai, Claroline, Atutor, and Olat). Morea provides a small subset of the capabilities of these systems, but is oriented toward the needs of institutions rather than individual teachers.
Metacademy is a site for community curated educational content. Unlike Morea, Metacademy supports a single version of curriculum material for any given topic. In contrast, Morea tries to make it as easy as possible for each educator to have their own, slightly (or radically) different version of curriculum material for any given topic. It's much like the difference between centralized version control (i.e. SVN) where there is always a single "golden" version of a system, and distributed version control (i.e. git) where there can be many "different but equal" versions of a system.
Laulima is a custom LMS for the University of Hawaii based on Sakai. Laulima does not implement the MOREA Pedagogical Pattern and so there is no ability to manipulate Modules, Readings, and so forth as "first class entities". This makes it difficult to (for example) support "Prerequisite Modules". In addition, Laulima implements a "pay wall", making content difficult to access or discover. Finally, the use of WYSIWYG editors makes it more difficult to reuse or export course content. That said, Laulima does provide useful support for grading and assignment management. In practice, users of Morea at the University of Hawaii typically use both tools: Morea for course content, and Laulima for assignment and course grading.
If you know of a related system, please let us know and we'll include it here.