If it is an FTI chip inside that unit, you could maybe use the open dmx object for the enttec unit as that is a very common serial to dmx chip used by many companies.
On the website for sunlight it says the developer kit comes with C++ examples of drivers. If you have to, you could use visual studio to compile an external for max. Check out the MaxSDK help file on creating your own externals. It walks you through the file structure and compiling process for a few different code compilers including visual studio.