Knock-offs are explicitly encouraged: https://gitorious.org/learn-x-the-hard-way/learn-x-the-hard-way https://gitorious.org/learn-x-the-hard-way/learn-x-the-ha

Knock-offs are explicitly encouraged: https://gitorious.org/learn-x-the-hard-way/learn-x-the-hard-way https://gitorious.org/learn-x-the-hard-way/learn-x-the-hard-...