Well it depends. If the customer is writing files themselves to the device, like over USB mass storage, then it'll work fine... It'll be their OS that does the long filename writing. Reading long filenames isn't covered in the patents.
If they are transmitting filenames over wireless, MTP (media transfer protocol), Pictbridge, or something like that then the system can write to a non-FAT filesystem easily enough that supports long filenames.
Trouble comes when you want to support a combination of things.. like support USB Mass storage AND MTP.