It is originally AWS, though we forked Firecracker ~4 years ago now and maintain an internal version with custom hypercalls (command-and-control from within the VM, POSIX-style fork, etc.) and a number of other features. We regularly pull patches and fixes from upstream Firecracker. You can read about the differences here:
replyfargate is not firecracker
replycan confirm that this is true for the fargate product used by consumers.
replyas someone who worked on it