What is the license of included sound files?

[v_mil]

Dear members! I can not find a license information of sound files in /usr/share/sounds/gnome/defaults/ : bark.ogg, drip.ogg, glass.ogg, sonar.ogg. What is the license of these files. Can I include one of these files as a part of my alert sound files for my free-of-charge programs? For example, can I combine 3 barks and verbal error description in my .OGG file for a program? With best regards. Viktor.

[Frogs Hair]

Ubuntu is GNU so the default sounds would also be. http://www.gnu.org/

[v_mil]

Many thanks!