> There is nothing stopping the Linux/BSD community from implementing something similar.
I don't meant to sound negative but wouldn't bots just be able to abuse any FLOSS implementation since they can then fake certain interactions with CloudFlare in the background?
>>gianca+(OP)
That would still introduce an asymmetric work aspect (presuming that Pat's are cheap to verify, difficult to mint, and single use only). Many bot-based attacks in the wild today rely on the fact that it is much cheaper for a client to send a request than it is for a server to handle one. A well-designed Pat system could flip that imbalance.