There is no way to answer this question without seeing the form and having an understanding of what liability you are releasing, and what liabilities you might be assuming.
I agree with the previous answer and it is hard to say. Traditionally you would need the approval of all lien holders and if not you could get stuck with a second mortagage if there is one. Take the paperwork to a lawyer before signing anything.
Only If and until you and I sign an Agreement for Legal Services, I am not your attorney. These answers are provided for informational and/or novelty purposes
I agree with the previous answers. Short sales are popular now but can be riddled with issues. If it is not your current primary residence could it be viewed as investment property and will you get taxed on the loss as 1099c income at the end of the year. Find an attorney in your jurisdiction that understands short sales and also taxes. Pay to have the document reviewed and be fully informed if you sign the document.