Having access to the source code allows the developer to make modifications to suit his customers' needs. Object code is computer code that other programs can hook on to on the front end or the back end without changing the original code. Some RIPs, like Onyx for example, use the interpreter just to translate the PostScript file and build a TIFF file, and use proprietary software on either side to do the rest. It's a Colorful World Something else to keep in mind while shopping for your RIP is its color calibration and correction capabilities. You'll need both to create quality output.
Calibration refers to the process of getting consistent color output.
Some RIPs, like Cactus, contain special software that lets you manually calibrate your equipment with external devices like colorimeters and densitometers. For instance, if a customer gives you a proof of a poster, and what you print out doesn't quite match, you'll want to correct the color. What kind of color correction will work best for you may depend on what you're used to. In the RIP software evaluations we have been performing in our lab, I have found a wide range of different styles of color correction, some easier to use than others. For instance, some RIPs have PhotoShop-style curves and percentages, which I found a little difficult to understand.