Zuul is described as 'program that drives continuous integration, delivery, and deployment systems with a focus on project gating and interrelated projects'. There are more than 10 alternatives to Zuul for a variety of platforms, including Linux, Online / Web-based, Windows, Mac and Self-Hosted solutions. The best alternative is Jenkins, which is both free and Open Source. Other great apps like Zuul are Travis CI (Freemium), Buildbot (Free, Open Source), JetBrains TeamCity (Free Personal) and CircleCI (Freemium).
Jenkins is a fork of Hudson and is a continuous build system for software projects. The leading open source automation server, Jenkins provides hundreds of plugins to support building, deploying and automating any project.
Travis CI is a leading provider of continuous integration and delivery services and empowers software development teams to test and deploy their applications with confidence. Teams can easily sync their cloud platform projects with Travis CI to begin testing code in minutes.
TeamCity is a continuous integration and build management system. With TeamCity, you can set up a build server within minutes and enjoy out of the box continuous unit testing, code quality analysis, and early reporting on build problems — even without leaving your favorite IDE.