Pmwiki is fairly minimalist. It will let you shape content to a great extent, but if you want interactive features, you have to install plug-ins. It's usually very easy to install plug-ins such as calendars, contact forms,and even shopping carts ranging from extremely simple to extraordinaire Lee complex.

The system is written in PHP, HTML, CSS, with the odd bit of JavaScript thrown in for good measure.  although no content management system actually fulfills its promise of allowing you to install and use without knowing any code, pmwiki is extremely easy to teach in terms of how it uses its own proprietary tag structure to format content.  It would be entirely reasonable to expect that many people could come in and collaborate on building content for a site using pmwiki once an administrator has set things up the way the group likes it.

The largest accessibility issue I've ever come across with pmwiki is that it's recaptcha plug-in is not accessible.  since this feature should never be implemented on any website under any circumstances, it would be no great loss if it wasn't for the fact that so many pmwiki designers feel the need to use it.  other minor issues such as images and objects not being tagged properly can easily be fixed in code.

Best,

Erik