Microsoft not only likes Linux, it also likes Java, since many cloud apps use Java & Linux.
Based on this podcast interview, apparently there is a license fee paid to Oracle for using Java.
Microsoft is apparently the largest distributor of Java licensing for Oracle,
and at the same time offering alternative free versions of Java are also usable on Azure.
Episode 145 - Java on Azure
Zulu - Azul Systems, Inc. Azul Systems, Inc.
"Zulu: certified builds of OpenJDK that can be deployed across various operating systems, containers, hypervisors and Cloud platforms. Choose Zulu Enterprise for cost-effective Java support."
Free Java implementations - Wikipedia, the free encyclopedia
Create a Java web app in Azure App Service | Microsoft Azure
Java developer center | Microsoft Azure