Marketplaces for distributing software products and services have been getting increasing popularity. GitHub, which is most known for its version control functionality through Git, launched its own marketplace in 2017. GitHub Marketplace hosts third party apps and actions to automate workflows in software teams. Currently, this marketplace hosts 440 Apps and 7,878 Actions across 32 different categories. Overall, 419 Third party developers released their apps on this platform which 111 distinct customers adopted. The popularity and accessibility of GitHub projects have made this platform and the projects hosted on it one of the most frequent subjects for experimentation in the software engineering research. A simple Google Scholar search shows that 24,100 Research papers have discussed GitHub within the Software Engineering field since 2017, but none have looked into the marketplace. The GitHub Marketplace provides a unique source of information on the tools used by the practitioners in the Open Source Software (OSS) ecosystem for automating their project's workflow. In this study, we (i) mine and provide a descriptive overview of the GitHub Marketplace, (ii) perform a systematic mapping of research studies in automation for open source software, and (iii) compare the state of the art with the state of the practice on the automation tools. We conclude the paper by discussing the potential of GitHub Marketplace for knowledge mobilization and collaboration within the field. This is the first study on the GitHub Marketplace in the field.