Basically, you are buying an operating system and source code and developing your I/O around their core. The I/O lines are what you would configure as inputs and outputs...tying optoisolators / output devices to the lines and controlling them with their processor and operating system.
Something like this only makes sense if you are going to be producing thousands of units. You have design costs, prototyping costs and testing costs before you even get to production costs.
We have an article on our web site that compares various methods when considering a controller for your application.