Hi,
ATOS SIPS, CM-CIC, PayBox are integrated by the different French banks for their clients.
If your NPO (non-profit organisation, association in French) has a bank account with a French bank, then you should contact them and see with them if you can setup a merchant account with them. They will tell you that you can use one of these payment plugins with your merchant account to accept payments to your bank account with them.
Otherwise, you can also use PayPal even if you're an NPO. You can read more about that here:
www.paypal-community.com/t5/Les-Archives...?profile.language=fr
I'm sure many other payment gateways offer solutions for NPOs.