Cela fait quatre fois que le destin me ramène devant cet article de Joël et je pense qu'il l'a écrit pour moi. Je note ici les phrases clefs :

Well, yes. They did. They did it by making the single worst strategic mistake that any software company can make: They decided to rewrite the code from scratch.
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It’s harder to read code than to write it.
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The idea that new code is better than old is patently absurd. Old code has been used. It has been tested. Lots of bugs have been found, and they’ve been fixed. There’s nothing wrong with it. It doesn’t acquire bugs just by sitting around on your hard drive. Au contraire, baby! Is software supposed to be like an old Dodge Dart, that rusts just sitting in the garage? Is software like a teddy bear that’s kind of gross if it’s not made out of all new material?

Voilà, reuse, adapt but do not rewrite it mothafucka !