On Mac OS X, the Credits ("LibreOffice Danksagung..." in German) dialog does not open in the help menu. Maybe it's redundant to the entry existing per default in the "LibreOffice" menu special to OS X ("Über LibreOffice")?
I WIN it's not a dialog, but a LibO document
"C:\Program Files (x86)\LibreOffice 3CREDITS.odt", what seems to show a snapshot of <http://www.libreoffice.org/about-us/credits/>
*** Bug 34609 has been marked as a duplicate of this bug. ***
Hints for a solution can be find in
Bug 34609 - Show License button and LibreOffice Credits do nothing Comment 5
*** Bug 38467 has been marked as a duplicate of this bug. ***
Comment from Thom Brown:
> I can see both LICENSE.odt and CREDITS.odt in
> If I copy them up a level to Contents, they both work.
Found this fixed in 3.5.0 and beyond. Likely a sideeffect of sberg's 3layer cleanup.
Fixed in -3-4 => will be in 3.4.6 => set target accordingly.