The contents of the platform specific packages are:
Solaris, Linux, AIX:
README.txt
libpassthrough.so (the NSAPI shared object, or “plug-in”)
HP-UX:
README.txt
libpassthrough.sl (the NSAPI shared object, or “plug-in”)
Windows:
README.txt
passthrough.dll (the NSAPI shared object, or “plug-in”)