Either Hamas has desecrated the mosque by storing bombs there or Islam allows bombs to be stored in mosques.
The text up at YouTube reads:
The Israel Air Force launches a precision strike against weapons hidden in a Gaza mosque on 1 Jan 2009. The secondary explosion caused by the ignition of the weapons cache proves the deliberate use of a place of worship as a military facility. Hamas uses the Palestinian people as human shields and exploits religion in its brutal campaign against innocent civilians.
Hat Tip to LGF again