The Incutio XML-RPC library (IXR) is designed primarily for ease of use. It incorporates both client and server classes, and is designed to hide as much of the workings of XML-RPC from the user as possible.
MiniXML provides a simple, API to generating and parsing XML. Its advantages are ease-of-use and the fact that no additional libraries are required. It comes with two independent implementations, 100% PHP and 100% Perl, which you can use separately.
widgEditor is an easily installed, easily customisable WYSIWYG editor for simple content. It replaces existing textareas with an improved editing pane using JavaScript, therefore if you don't have JavaScript (or your browser doesn't support HTML editing) it degrades gracefully.
Usually, programs are written and documented in English, and use English at execution time for interacting with users. This is true not only from within GNU but also in a great deal of proprietary and free software.