MindTouch SDK

DekiScript

If you need to automate content in a wiki page by gathering data from multiple sources and then presenting it nicely, DekiScript is the tool to use.

DekiScript is a scripting language that can be used directly in wiki pages.  It requires no server-side access and ties directly into MindTouch's built-in security system.  DekiScript can be shared as code snippets, templates, or extensions.

Don't use DekiScript if you need to store or modify data.  DekiScript is only intended for presenting information without modifying it.

PHP

If you need to customize MindTouch's User Interface and the work absolutely needs to be done server-side, then PHP is your best first choice.

MindTouch has a PHP plug-in framework that makes it easy to add custom behavior without having to modify shipping source code.  This means, your customizations will continue to work even when your MindTouch site is upgraded.

Don't use PHP for extension or if you need to interact with enterprise systems (e.g. SOAP web-services).

JavaScript

If you need to show pop-up dialogs, dynamically refresh content in pages without reloading the page, or otherwise create rich workflow experiences, then JavaScript is your best tool.

MindTouch ships with an extensive JavaScript library including jQuery, fckEditor, and others.  JavaScript files can either be installed server-side or be dynamically loaded through extensions.

Don't use JavaScript to embed read-only information since it won't be indexed, or access privileged APIs since these calls could be easily be abused.

C# (.Net/Mono)

If you need to integrate with a database, another enterprise system, or need to build web-services for your solution, then your best choice is MindTouch's .Net/Mono libraries written in C#.

MindTouch includes a cross-platform web-services runtime called Dream.  Dream makes it easy to write RESTful web-services that expose data for JSON, XML, or PHP clients.  Web-services written with Dream comply by-design with MindTouch's web-oriented archicture (WOA).

Don't use C# if you need a simple extension that takes parameters, transforms them, and then presents the result without storing or updating any state information.  And don't use C# if you have an aversion to compiled languages. ;)