Context:

I’m trying to understand the concept of vendors in the Java ecosystem.

When I started learning Java, I thought it was a single entity with versions like Java 8, Java 11, etc. Later, I discovered that multiple vendors release their own distributions of Java, and now I’m confused about how this works.

Here are my main questions:

Are different vendors’ Java distributions truly different?

• Do they use/write different source code? For example, does something fundamental like the serialization mechanism or Object#toString implementation vary between vendors?
• How do they ensure compatibility with the same set of features? For example classes have the same packages, methods have the same return types, …

Who controls the overall direction of Java?

• Who decides/prioritizes what features to introduce in a new Java version?
• How are deadlines and release schedules determined?
• What if one of the vendors is slow implementing feature, another’s performant
• What if one of the vendors realizes that it lacks competence to implement a feature.
• Can anyone become a Java vendor?

Who are these vendors:

• Hypothetically, what would it take Homer Simpson to run his own Java distribution?
• What motivates companies to maintain their own Java distributions? (e.g. JetBrains has its own Java distribution)
• How do these vendors generate revenue from something that’s open
  source and freely available?