Poseidon V4.4, available since February last year, has no longer any keyfile protection or similar code in it. If you want to use it with the spider.device, I'm not stopping you from. If it doesn't work due to bugs in the spider.device, you should contact Elbox for an updated driver. Apart from removing the "compatibility hack" in the V4.x versions (which simply did not send the reset command to the driver at start), I do not see any reasons why it shouldn't work.
You won't get "proper" USB 2.0 support though (regarding split transfers and such), but rather the way it was in Poseidon V2.x/V3.x, because as far as I know Elbox has not updated their driver in that direction. The docs how to do this are in the AROS repository.
This is as far as my support for the Spider gets.
How about the ArakAttack driver for amithlon? I purchased that driver, although it was for poseidon 3.x i believe. Have to see if it would work with poseidon 4.x on my amithlon system.