Mainframes are among computing’s oldest platforms, but they remain deeply embedded in industries such as banking, insurance, retail and government. For developers building and maintaining the software that runs on them, getting access to real mainframe environments to test their code can be difficult.

The Linux Foundation’s Open Mainframe Project is making that access easier. The project recently announced that shared mainframe infrastructure is now available to approved open source projects for development, testing and education. The infrastructure supports Linux-based workloads on IBM Z, z/OS and cloud-native technologies, the project said in an announcement.

For many software projects, developers can reproduce a target environment locally or spin it up in the cloud. But mainframe contributors may have fewer opportunities to validate their code on the operating systems and hardware it is designed to run on. The shared infrastructure gives open source projects access to those environments for testing while also providing practical experience that documentation and virtual environments alone cannot replicate, the project said.

John Mertic, director of program management at the Linux Foundation, described the launch as an important step for the Open Mainframe Project’s developer community.

“What’s particularly exciting is seeing this infrastructure move from an idea into something contributors can actually use,” Mertic wrote. “It also creates more opportunities for people to participate in the community, learn from one another and contribute to the technologies that support today’s mainframe ecosystem.”

Getting to this point took several years. Broadcom donated an IBM z15 system to the Open Mainframe Project in 2022, with plans to make it available for development and testing beginning in 2023, but the rollout took longer than expected. By the end of 2024, the system had been delivered to Marist College but was still awaiting installation. In February 2025, the Technical Advisory Council still listed collaboration with Marist and funding as challenges facing the infrastructure effort. That April, the council ranked getting the mainframe infrastructure running as its top strategic priority.

The latest announcement no longer frames the infrastructure around a single donated machine. The Open Mainframe Project thanked both Broadcom and IBM for providing access to mainframe systems, but did not detail the exact hardware behind the available environments.

The first two projects using the infrastructure show the range of mainframe software it could support. Feilong is a cloud connector that uses REST APIs to automate virtual machine management on z/VM and connect it to tools such as OpenStack and Terraform. CBT Tape sits at the other end of the mainframe timeline. The project traces its roots to 1975 and maintains a large collection of free utilities for IBM mainframe operating systems, including z/OS.

The Open Mainframe Project said it plans to make the resources available to additional open source projects over time. Interested communities can apply for access through the Open Mainframe Project Technical Advisory Council.

The rollout fits into a larger effort to bring open source development practices to the mainframe. The Linux Foundation launched the Open Mainframe Project in 2015, and its work now includes projects focused on testing, hybrid cloud integration, observability, development tools and education. Providing access to real mainframe environments is another step toward helping more contributors take part in that work.