Top 9 JVM and JDK Open-Source Projects

Graal

156 19,748 10.0 Java

GraalVM compiles Java applications into native executables that start instantly, scale fast, and use fewer compute resources 🚀

Project mention: Java 23: The New Features Are Officially Announced | news.ycombinator.com | 2024-04-17

Contrary to what vocal Kotlin advocates might believe, Kotlin only matters on Android, and that is thanks to Google pushing it no matter what.
https://spectrum.ieee.org/the-top-programming-languages-2023
https://snyk.io/reports/jvm-ecosystem-report-2021/
And even so, they had to conceed Android and Kotlin on their own, without the Java ecosystem aren't really much useful, thus ART is now updatable via Play Store, and currently supports OpenJDK 17 LTS on Android 12 and later devices.
As for your question regarding numbers, mostly Java 74.6%, C++ 13.7%, on the OpenJDK, other JVM implementations differ, e.g. GraalVM is mostly Java 91.8%, C 3.6%.
https://github.com/openjdk/jdk
https://github.com/oracle/graal
Two examples from many others, https://en.wikipedia.org/wiki/List_of_Java_virtual_machines
Dragonwell8

4 4,092 8.3 Java

Alibaba Dragonwell8 JDK
InfluxDB

www.influxdata.com
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Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
OpenJ9

7 3,215 9.9 Java

Eclipse OpenJ9: A Java Virtual Machine for OpenJDK that's optimized for small footprint, fast start-up, and high throughput. Builds on Eclipse OMR (https://github.com/eclipse/omr) and combines with the Extensions for OpenJDK for OpenJ9 repo.
Avian

2 1,214 0.0 C++

[INACTIVE] Avian is a lightweight virtual machine and class library designed to provide a useful subset of Java's features, suitable for building self-contained applications.
Adopt Open JDK

2 993 9.1 Shell

Eclipse Temurin™ build scripts - common across all releases/versions
ParparVM

0 953 -
SAP Machine

1 484 10.0 Java

An OpenJDK release maintained and supported by SAP

Project mention: What's the business thinking behind so many different OpenJDK builds by different vendors? | /r/java | 2023-05-01

SapMachine has specific changes that is used in their Cloud platforms. https://github.com/SAP/SapMachine/wiki/Differences-between-SapMachine-and-OpenJDK
WorkOS

workos.com
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The modern identity platform for B2B SaaS. The APIs are flexible and easy-to-use, supporting authentication, user identity, and complex enterprise features like SSO and SCIM provisioning.
openjdk

89 304 5.5

Microsoft Build of OpenJDK (by microsoft)

Project mention: Microsoft seeks Rust developers to rewrite core C# code | news.ycombinator.com | 2024-02-03

They use a ton of java, they even have their own distro. In fact, they answer this question on its landing page (https://www.microsoft.com/openjdk):
> Java at Microsoft spans from Azure to Minecraft, across SQL Server to Visual Studio Code, LinkedIn and beyond! We use more Java than one can imagine.
Liberica JDK

2 280 6.3 Dockerfile

Free and 100% open source Progressive Java Runtime for modern Java™ deployments supported by a leading OpenJDK contributor

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020). The latest post mention was on 2024-04-17.