Unfortunately, the 4kus website seems to have mislabeled this firmware update. It does not support bitsetting
Unfortunately, Recently, 4KUS (a Liteon OEM) released firmware update version ESG4 for their DRW-1S40, which is a rebadged Liteon LDW-401S. The changes in this update are said to be this: "Add support for BookType / BitSetting techniques" This means that 401S users who don't want to take the risk of converting their drives can now use bitsetting in hopes of improving the compatibility of their burned discs in DVD Players. The firmware build date is fairly old (2003/11/25 10:56) but is newer than the current latest official LDW-401S firmware, ES0J.
I've modified ESG4 to contain the LITE-ON DVD+RW LDW-401S name and the flash tool to flash both the LDW-401S and the DRW-1S40. I can't try it myself, so please let me know if you try it and it works.
Get it here: http://dhc014.rpc-1.com/indexOEM.htm#LDW-401S