That's a _very_ incorrect statement. You can use any OpenJDK (which is GPLv2 with classpath exception) distribution you want to run Apache Zookeeper without having to have any agreement with Oracle or pay any fee. The Oracle JDK is just Oracle's commercial version of their OpenJDK distribution with Oracle support.

You can use the OpenJDK distro shipped in your Linux distro (RedHat, Debian, etc.), you can use Microsoft's OpenJDK distro[1], you can use the Eclipse OpenJDK distro, you can use Amazon's OpenJDK distro [3] and there are a whole bunch more.

[1] https://www.microsoft.com/openjdk [2] https://adoptium.net/ [3] https://aws.amazon.com/corretto/