Bought a €15 card off ebay, registered on website from the US per the instructions earlier in the thread, and received a txt (to the orange number) almost immediately while on t-mobile. Emailed a passport scan to
blois.contrats@orange.com. No idea if someone is now out there stealing my identity but seemed to activate the card after a few days and no less safe than someone making a copy or taking the number down.
For the first day or two the site showed only a €5 credit then seemed to fully activate and show €15 in credit. Used the menu for 50Mb (50Mo) of internet for €2 per day. Only have to do this once per day as I made a mistake one morning and I think it deducted twice. Orange sent a txt when my previous day ran out.
All-in-all, pretty happy with this for a week in FR despite the bit of effort needed. Very helpful to have the phone and internet while wandering around.