The SAS .dll files are essentially the compiled components of SAS. They are not "openable" except by programmers at SAS who are doing maintenance or development.
In the "old" days, for example, when I wrote a COBOL program, I had to compile, link and load the program in 3 separate steps before I could run the program. These days, most .dll files are smaller, already-compiled, already-linked programs and sub-routines that are called when they're needed by a main program.
Generally speaking, you should not need to "look inside" or open any of the SAS .dll files. If you are having trouble with a SAS process or procedure, you can contact SAS Tech Support for help with that procedure. If you think you have uncovered an anomaly in the way SAS is working, Tech Support can take note of your problem and alert the developers if they need to make changes.