They stopped supporting old devices. Such a shame... Some guy sold me 2 plugins on Ebay. Just search 'Archos plugins' there and you will find a seller nelly1337 selling Android plugin.
I just asked him about gen4 plugins. Let's wait a bit for his answer.
But I have another way. I have Archos 704 wifi and want to unlock those two by applying the ones bought for 504. I unlocked Videopodcast and Cinema on 4 different 504 devices with only 2 files. Look here viewtopic.php?f=18&t=70333
So I need your help and later I could help you in return. I need an old firmware to unlock my 704 from its hard drive. What firmware version do you use?