It was the dongle they made that had it. It stole parts of Atmosphere's code to run their custom SX OS and if you tried to reverse engineer it it would brick your console upon putting it back in.

Most DS flashcarts had time bombs that would make them stop working after 2 years, though I think the one on the 3DS also had a prevention that would brick your console as well but I'm not sure

Did you mean musescore.com? Because the ".org" site is only for downloading the software. Be warned that you'll need this tool if you want to download anything for free