As far as I can read in https://fr.ulule.com/about/terms/, paragraph 4.3.1...

Payment by credit card is automatically processed but if the project fails to raise enough money, the money is transferred to your electronic money account inside Ulule, that you can use then for another project or you can ask for reimbursement (for free).

Also, up to the end of the period of the money raising, you can cancel your participation...

Note that Ulule is quite known here for being a serious company, usually selecting projects seriously, and with a great percentage of success.

Feel free to ask more questions!