Frankly, this attitude is exactly the problem with the JOSM program. I’ve been coding Java for over 20 years myself (i.e. Java 5 was released during my professional career), and I’ve transitioned from CVS to SVN to git, ant/maven/gradle build systems, the rise of CI, many different enterprise frameworks, etc etc. The world has changed over these years and JOSM is stuck in a time warp by, and I’m struggling to keep this within the etiquette guidelines, leaders that throw up every possible roadblock against anything new.
Yes, you are losing developers that would otherwise contribute. You have a silly versioning system, refuse to move off SVN and patches, your awful bug reporting system, archaic wiki, perpetually out of date layer index, and a general hostility to any new technology which the rest of the open source software development world now regards as normal and expected.
You do not see the people that aren’t contributing. You don’t see them because they’re not there, and they’ve chosen to spend their valuable free time on other projects, where their skills are welcome.
Yes, it is stable. Fortran 77 is stable. And stability alone does not equate to progress. Stability without adaptability leads to irrelevance. JOSM may function well at a user level for those who have been using it for decades, but that does not mean it is a healthy, thriving open-source project.
A strong open-source ecosystem thrives on contributions, not gatekeeping. Modern developers expect streamlined workflows and maintainers who encourage innovation rather than dismiss it. The idea that “if you can’t figure out our outdated and convoluted setup, you shouldn’t contribute” is both self-defeating and a surefire way to guarantee stagnation.
If the goal is to preserve JOSM as a functional but increasingly legacy tool maintained by an ever-dwindling group, then by all means, continue resisting change. But if the intent is to build a sustainable project that remains relevant and attracts new contributors, then the hostility toward modern software practices needs to stop.