void addUrls(KURL::List urls)
void addUrl(KURL url)
void burn()

K3b offers the K3bProjectInterface as listed above or the more powerful K3bDataProjectInterface which only applies to data projects (CD and DVD):

void createFolder(QString name)
void createFolder(QString name,QString parent)
void addUrl(KURL url,QString parent)
void addUrls(KURL::List urls,QString parent)
void removeItem(QString path)
void renameItem(QString path,QString newName)
void setVolumeID(QString id)

Using this it is possible to fill a data project with files and folders from a script. The following script for example creates a new data project, adds several folders to the project, and adds files to the newly created folders:

#!/bin/bash
PROJECT=$(dcop k3b K3bInterface createDataCDProject)
dcop $PROJECT createFolder test
dcop $PROJECT createFolder foo
dcop $PROJECT createFolder bar /foo
dcop $PROJECT addUrl /home/trueg/somefile.txt /foo/bar