The spelling you see probably just indicates the way the person using that spelling pronounces it- "Ooh-samah bin Lah-den" is a typical American way to pronounce it and is usually spelled as "Osama bin Laden". read more
the Arabic alphabet differs from the Latin alphabet. The Arabic alphabet has 28 letters rather than 26, and it uses completely different characters—some of which, including the first character of Bin Laden's first name, do not have directly corresponding sounds in English. read more