Marble is a virtual globe and world atlas — your Swiss army knife for maps. Find your way and explore the world! 

Currently the Marble KDE application stores the owncloud password as plain text in its configuration file. See marble_part.cpp:
cloudSyncManager->setOwncloudPassword( MarbleSettings::owncloudPassword() );
Change that to use kwallet for storing the password. See e.g. http://techbase.kde.org/Development/Tutorials/KWallet

Helpful links:

• https://bugs.kde.org/show_bug.cgi?id=327978
• The easiest way to reach Marble developers to help you is to visit the #marble IRC channel in freenode. Watch out for Earthwings
• http://marble.kde.org/