Tax credits can be refundable or non-refundable.
Non-refundable credits are only good against your actual tax bill. Refundable credits, as their name implies, do allow such refunds. HOPE does come with a few strings attached. In addition, students who have been convicted of a felony for the possession or distribution of a controlled substance are ineligible. And, students who receive other forms of financial aid such as a Pell Grant will have the amount of their eligibility for HOPE reduced by the amount of aid they receive.