The Nastaliq Navees ("Nastaliq Writer") font package provides the capability to render Arabic, Urdu, and related languages in the Nastaliq style of calligraphy. This is achieved through the use of QuickDraw GX, which allows fonts to define complex behaviors where the glyph used to render any particular character is determined by the surrounding characters; thus, any given letter in Nastaliq Navees may take on many different forms in order to join appropriately to its neighbours. Nastaliq Navees should work with any application which supports QuickDraw GX typography.
Please note, this font is not Unicode-encoded. SIL's Unicode fonts for Arabic are available from their  Arabic Script Unicode Fonts page.