Mellivora is described as 'mellivora - Mellivora is a CTF engine written in PHP' and is an app in the Development category. There are four alternatives to Mellivora for Self-Hosted solutions, Docker, Linux and Ruby. The best alternative is Hack the Arch, which is both free and Open Source. Other great apps like Mellivora are MITRE CTF Scoreboard (Free, Open Source), CTFd (Paid, Open Source) and BOCA Online Contest (Free, Open Source).
Although each local site runs its competition independently (for example, the programming environment and the submission systems are controlled locally), the problem set and test cases are prepared by a unique committee