Legal implications part: Distributing keys via GitHub infringes on copyrights. Developers could face lawsuits, bans from GitHub, and damage to reputation. Users might lose access to support and updates.
For those looking for free or open-source alternatives, there are several slider plugins available for WordPress, such as: slider revolution license key github
Yes, ThemePunch offers a of Slider Revolution on the official WordPress plugin repository. It is not as feature-rich as the premium version, but it includes: bans from GitHub