You may be surprised to hear that the dominant public Internet wiki engine, MediaWiki, only plays a minor role in the enterprise. Within the corporate firewalls, TWiki, Confluence, DokuWiki, TikiWiki, and others are running the show. Why is that? It is certainly not the lack of commercial customer interest in MediaWiki, which everyone already knows as the software running Wikipedia. It is also not an anti-commercial stance by the creators of MediaWiki (and its effective owner, the Wikimedia Foundation).
From what I can tell, companies are shying away from bringing commercial innovation and investment to MediaWiki because of the uncertainty around its intellectual property. I recently talked with a consulting firm that intends to provide services and extensions to MediaWiki. Extension is the MediaWiki term for plug-in, that is program code separate from the main project code but that is executed together with it. When they asked their lawyers whether they could create and sell proprietary extensions to MediaWiki they received a lawyerly “maybe”, which left them wondering whether it would be wise to bank on MediaWiki.
MediaWiki uses the GPLv2 (and later) license family. Whether the GPL applies to extensions has been answered by the community a couple of times with a not-so-resounding “probably not”. Thus, software firms are somewhat left guessing as to the legal situation and the intentions of the MediaWiki development community. Being able to decide on your own when you want to open source or keep something proprietary, however, is key to engaging software firms and creating commercial investment and innovation.
At WikiSym 2010 I talked to a lot of Wikimedia Foundation (WMF) folks. The WMF operates Wikipedia and is the caretaker of MediaWiki. From these discussions I know that the WMF guys want commercial innovation around MediaWiki and are not at all fundamentalists about open-sourcing everything that touches MediaWiki. So here is what I think needs to happen if we want to see MediaWiki benefit from commercial innovation and have it make inroads into the enterprise:
- Exception clause. There must be legal certainty as to whether extensions/plugins can be kept proprietary. The way to go is a clearly defined exception clause to the GPL that covers extensions. It must be safe for a firm to innovate and keep the fruits of their labor for a while. I don’t worry about not sharing: In most cases, competitors and community will catch-up fast enough so that nobody will keep software proprietary for too long.
- Trademarks and other IP. The term “MediaWiki” is important from a marketing perspective due to spill-over effects from Wikipedia. Thus it must be crystal-clear under what circumstances a software firm can use this term in its marketing outreach. The usual solution is to create a foundation, say, the MediaWiki Foundation, which becomes the caretaker of the trademark and other IP, and in which commercial entities can have a stake. 
The second bullet item suggests the creation of a MediaWiki Foundation. One may wonder whether the Wikimedia Foundation can play this role. I wouldn’t advise this, because conflict of interest resolution would be difficult in such a setup. The primary mission of the Wikimedia Foundation is to steer and operate a specific set of services, and MediaWiki is just the software being used for it. If firms would always fear having to bow to WMF interests when the going gets tough, they’d stay away from the get-go, as they are doing today.
Another alternative would be to transfer rights to a software foundation like the Free Software Foundation (due to GPL) or maybe the Apache Software Foundation if folks were to consider a license change. These foundations are experienced in handling conflicts and might be good caretakers. On the other hand, as the Drupal Foundation shows by comparison, MediaWiki may well be important enough to warrant its own foundation.