I dont see why not, as long as you make sure that the disclaimer is visible to them and that they know what they are liable for etc etc. It would be like when you install software and they come up with a "Terms & Conditions" statement that you have to click on "I agree....." in order to move on. Just make sure the person signing up is aware of the terms / conditions and state that by clicking on the "I agree" checkbox, they are pretty much signing the form.