Well, they may have been written already, but there may be pitfalls beyond combinatorics (possibly exaggerated for dramatic effect): one part of the code you'd

Well, they may have been written already, but there may be pitfalls beyond combinatorics (possibly exaggerated for dramatic effect): one part of the code you'd like to reuse works wonders, but it is written as an all-too-clever abuse of PHP4, under an unclear license; another is a closed-source library which may or may not exist for all your target platforms; and yet another is a custom-license Python 2.6 script. Now how do you reuse those; and btw what license will you use for the result? This is not Pokemon, where you just need to "catch 'em all" and you're set; integrating the pieces together could be the most expensive part.