The only thing I can find suggests it's based on tiff. Maybe you could try hacking the magic word and seeing if a standard tiff library will read it?

Panasonic : RW2. Example or RAW. See ExifTool

    Intel byte ordering. TIFF magic word is 0x55 instead of 0x2a. Firs
+t IFD at offset 0x18 for RW2, 8 for RAW. No Makernote tag.
    full resolution image in IFD#0.
[download]