You are right, that is the native screen dpi.
But, I think, that applications that are running in 800x480 are designed with 240 dpi as standard. Dpi is nothing more that a constant of the device provided to applications for calculations of text font size and layout of controls . That is my guess and I find comfortable a dpi of 200 for this device.
See what happens in windows when you change system font size (dpi)!
History: Orange SPV c500, Qtek S200, HTC P3600, HTC Diamond, HTC TouchPro, HTC TouchPro 2, HTC HD2, Samsung Galaxy S, HTC DHD, Samsung Galaxy S2, Samsung Galaxy Note, Asus TF201, Samsung Galaxy Note 10.1, Samsung Galaxy Note 2.