Flashcarts don't affect the consoles, it's like if you were to take an empty DVD, put a movie on it and play it on your DVD player, the DVD player would play the movie but there wouldn't be any side effects. Same thing with flashcarts, you just put the games on them (or rather on the microSD card) and you can play them on the DS, but the DS itself won't change.
This post has been edited by Nathan, Sun, September 15th, 2013 at 12:27