I would like to use a HTTP proxy on top of Kafka. I see two projects with same purpose :
I use strimzi operator to spin up Kafka on Kubernetes.
How do they differ ? When to use which one ?
The licensing and nature of the projects are a bit different. Strimzi is an independent project under the Cloud Native Computing Foundation. And the Strimzi Bridge (and all other Strimzi components) is licensed under Apache License 2.0 as a recognized open-source license. The Confluent REST Proxy on the other hand uses a proprietary Confluent Community license - whether that works for you or not depends on how you use it.
On the other hand, if I remember correctly, the Confluent REST Proxy has more features around things such as topic and cluster management etc. For many use cases, both will do the job. But it is good to check what exact features you need as they might not support the same things.
The Strimzi Bridge is also directly supported by the Strimzi Operator. So if you already use it, it might be easier for you to stick with it. Similarly, if you would be already using the Confluent Platform, it might be easier to go with the Confluent REST proxy.
Disclaimer: I'm one of the Strimzi maintainers.