WMF project code
The Wikimedia Foundation indicates its projects with project codes; see also MediaWiki's language codes. These project codes are loosely related to the dominant standard for the identification of languages, the ISO-639. The problem with the project codes is that they are not consistent; they use what used to be Ethnologue codes and, they also include codes that were made up because what some people call a language is (or was) not (yet) considered a language by the standards bodies, or had simply not been registered at the point in time, when a wiki was created.
In the OmegaWiki project, we have a need for correctly identifying languages because the intention is that the data of OmegaWiki is useful to automated systems as well. This leads to a situation where the Wikimedia Foundation project codes are not useful because of the way they were made up. An additional problem is that it is not clear what the status of codes are; are they ISO-639-1, ISO-639-2, ISO-639-3, Ethnologue or made up. Some of the codes like als are incompatible with the ISO-639-3 standard.
By creating a link to the ISO-639-3 based portals on OmegaWiki and by linking to Ethnologue who maintain the ISO-639 code, we hope to inform about the status of many languages.. This works well for the majority of languages. There are however codes that used to be proper language codes, that have been changed to a different status in ISO-639-3 a good example is Chinese which is now considered a macro-language. Typically Chinese is Mandarin and Mandarin can be in either the simplified or the traditional script so in essence the zh and zho code can be replaced by the cmn code. It also means that there are now codes for languages like Min-nan, Yue etc.
All in all, separating project codes from the language codes is helpful because it allows for better access to automated systems. Without some special footwork, spiders will not be able to identify languages when they are marked in a non-standard way.