You can deploy Kafka using DC/IO and it takes care about HA for you. DC/IO is quickly becoming the go-to solution for database deployments. ArangoDB even recommends it as default.
Now about Kafka vs ZeroMQ: you want Kafka if you cannot tolerate the loss of even a single message. The append-only log with committed reader positions is a perfect fit for that.
Issues and projects are global and not bound to a single repository. In my experience, this is the only approach that works in a company. JIRA does the same thing.
It's the closest to a fully open source Atlassian suite that you get. Phabricator has code review, repository hosting, project management and even a CI tool.
Take a look at Phabricator. It's a former Facebook project and been battle-tested at very large companies for years now. Huge open source projects like Blender, Haskell, Wikimedia and LLVM use it since it's the best open source code review tool and issue tracker. Wikimedia had a lengthy decision process and thoroughly vetted the alternatives.
It has many enterprise features including code ownership, issue templates, and a Gerrit like, sane code review workflow. You can fully integrate it with your CI tool and it even displays coverage results inline and such.
Ask me anything about it :) I'm not affiliated with it but am an experienced user.