Hi, another Gardener here. Garden Core should indeed be enough to get started. I'm trying to keep this as factual and non-pitchy as possible for the sake of providing context—the enterprise product gets you:
• RBAC and secrets management (also makes it possible to control which users have access to which types of environments)
• Direct integration with GitHub or GitLab, so you could trigger something to happen in Garden based on a VCS event
Zeebe is indeed a Java application, but it's possible to use Zeebe without writing any Java. Broker operations can be managed with a CLI (https://github.com/zeebe-io/zbctl). Along with the Go client, there are experimental Node, Ruby, and C# clients, but these are community contributions that aren't yet officially supported by the project.
I'm on the team that's building Zeebe and want to mention that we release new "dev preview" versions on average once per month and are aiming to have a production ready 1.0 by the end of 2018. If anyone has questions or ideas, or wants to build a prototype with Zeebe, it'd be great to hear from you. There are various ways to contact us here: https://zeebe.io/community/
• RBAC and secrets management (also makes it possible to control which users have access to which types of environments)
• Direct integration with GitHub or GitLab, so you could trigger something to happen in Garden based on a VCS event
• Automated environment cleanup (coming soon)
• Support and all that