At the Wikipedia website there is a "WikiProject" pseudonamespace that places all content development projects inside the "Wikipedia:" namespace. At Wikipedia, all content development projects have page names that start with "Wikipedia:WikiProject". Rather than use a pseudonamespace for content development projects, Wikiversity uses the "School:" and "Topic:" namespaces. For details about content development projects at Wikipedia, see w:Wikipedia:WikiProject.
Namespaces are a feature of the MediaWiki software that is used to power the WIkiversity website. The Wikiversity website has a large number of webpages. Namespaces provide a system for organizing all these Wikiversity webpages that would be otherwise disorganized and hard to work with. Wikiversity namespaces allow webpages with related functions to be neatly separated into compartments. You can think of each namespace as a compartment that holds a large group of functionally related pages.
A wiki could function with all of its webpages in only one "namespace", but wiki participants have found that the extra organizational structure provided by a set of namespaces makes it easier to manage the many pages of a wiki. The practice of dividing a wiki's pages into more than one namespace began as a way to keep the intended content pages of a wiki separated from pages that that are "meta pages". "Meta pages" are concerned with the operation of the wiki itself and the process by which its participants create the intended content pages. At Wikiversity, all learning resources and actual educational content is on webpages in the main namespace. Each page in the main namespace has an associated page in the "Talk:" namespace where Wikiversity participants can discuss the contents of the main namespace page. The talk pages are "meta pages" that are not actual learning resources, rather, the content of "Talk:" pages is "meta level content". When Wikipedians discovered the value of sorting wiki pages into multiple namespaces (each namespace with a defined use) they continued this fragmentation and invented additional namespaces such as the "Template:", "Category:" and "Portal:" namespaces.
One of the "meta-level" namespaces is called the "project namespace". The name of this namespace (project) does not mean that every wiki collaboration ("project") has to be in the "project namespace". Think of the Wikiversity "project namespace" as pages that are relevant to the entire wiki project. There is one particular wiki editing project that is the concern of the Wikiversity "project namespace"; it is the Wikimedia project called "Wikiversity". The "project namespace" at Wikipedia is also called the "Wikipedia:" namespace and all of its pages have names that start with the prefix "Wikipedia:". At Wikiversity, the "project namespace" is called the "Wikiversity:" namespace. This page has the page name "Wikiversity:WikiProject" and is a page in the "Wikiversity:" namespace. Like other pages in the "Wikiversity:" namespace, this page is concerned with how the entire Wikiversity project is organized.
Wikipedia puts its content development projects in their "project namespace", but Wikiversity does not use Wikipedia's clumsy "WikiProject" pseudomnamespace approach for forcing content development projects into a single namespace. Wikiversity allows content development projects for specific academic topics to exist in a special namespace that was invented at Wikiversity.
Special namespaces for content development
If you can accept the idea of having a new namespace specifically for content development projects, then you still might ask: why does Wikiversity have two namespaces for content development projects? The main reason that Wikiversity has both a "School:" namespace and a "Topic:" namespace is because wiki community members naturally create hierarchical systems to organize content development projects. At Wikipedia there are both "higher level" "WikiProject" pages such as WikiProject Science and "lower level" "WikiProject" pages such as WikiProject Molecular and Cellular Biology.
Wikiversity has both a "School:" and a "Topic:" namespace so that the "School:" namespace can be for a relatively small number of "higher level" content development pages that function to organize a larger number of "lower level" content development projects for narrow academic topic areas. Wikipedia has a relatively narrow mission: to produce encyclopedia articles. Wikipedia has a smaller range of possible main namespace content than does Wikiversity. Wikiversity should come to have many more content development projects than does Wikipedia. The hierarchical system of "School:" and "Topic:" pages will become increasingly useful as the number of Wikiversity content development projects continues to grow (see the list of "Topic:" pages).
Wikiversity currently has mostly school pages corresponding to university schools. In the future there will be many other types of Wikiversity schools that organize many kinds of content development projects in a large number of different ways. Ultimately, the Wikiversity "Topic:" namespace may become nearly as large as Wikipedia's main namespace. When Wikipedia's main namespace got too large, the "Portal:" namespace was invented. For the same reason that it makes sense to have the "Portal:" namespace to provide "directory" pages for the main namespace, it makes sense to have the "School:" namespace to provide "directory" pages for the "Topic:" namespace.
At Wikiversity, content development projects can be called "department", "center", "institute", "WikiProject", "content development project" or anything else that participants feel is a useful way to refer to a content development project. At Wikipedia, the content development projects ("WikiProjects") are all pages in the "Wikipedia:" namespace. At Wikiversity, the content development projects are mostly in the "Topic:" namespace while some "higher level" projects exist on the "School:" namespace and function to organize large groups of related "Topic:" pages.