The most common way to get the software "free" is by checking the packaging of a newly purchased TI-Nspire CX II CAS Go to product viewer dialog for this item.
Modern TI-Nspire software connects to TI servers to validate licenses. Cracked versions often block network access, which means you cannot download crucial OS updates for your physical calculator. If you update your physical calculator's OS to 5.0 or higher, your cracked PC software will stop recognizing it.
Getting the TI-Nspire CX CAS student software license free is easier than you think. Here are a few options: