Original Mustek drivers can be installed at most on Windows XP. You can find them there. They are no longer supported by the vendor.
Modified driver is based on the latest available original driver (package version is 1.3, kernel driver version is 2.6). It has a minimum required set of functionality (WIA interface). There is no TWAIN interface or helper fancy stuff.
The driver is provided "as is". Use it at your own risk.