Problems with Driver under 10.3

I need someone with some technical savy to help me figure out a way to get a driver to work under 10.3 that used to work under 10.2. When I try to install it under 10.3 it says it is not installed correctly although it used to work under 10.2. The driver is for a usb to serial adapter. The driver is at http://www.mct.com.tw/driver.html
but has not been updated in a long time. Is it possible to manually install parts of the package using the terminal and not the install package. Any help would be greatly appreciated. I am desperate as I need it as a major component of my work and do not want to reinstall 10.2. Thanks.