Being properly insured for WWOOFing activities is part of your commitments when you join the association. It is your responsibility to check with your insurance guarantees and exclusions of your policy. Your WWOOF France membership does not include insurance.
As a professional farmer or an individual, you must have an insurance policy that covers your property and activities performed on it. Do not hesitate to contact your insurer, since they know best the warranties and exclusions of your policy.
If you are an individual, your home insurance includes a "civil liability" that covers accidents that may be caused to others at your fault. You don’t need to take additional insurance to host WWOOFers.
If you are a professional, your home insurance includes a "civil liability" that covers accidents that may be caused to others at your fault. However, check with your insurance company and ask them to send you a certificate indicating that WWOOFers are also covered (MMA issues such certificates). WWOOFing is defined as a unpaid activity, just as volunteering or mutual farming assistance.