I have a penchant for old software that just works. Two of my favorite old programs are Adobe Photoshop 3.01 for Unix and Main Concepts Main Actor for Linux. Both were around early on and just never gained much traction. Both provided sorely needed desktop features that are still illusive to this day in my opinion. Some of this is due to the open plugin architecture that these programs provided. They created an ecosystem. I paid good money for features(plugins) I needed because it increased my workflow. It was also a way to differentiate your work from anothers in a cookie cutter world.
What commercial software that ran on open source was abandonded ahead of its time in your opinion?
What commercial software that ran on open source was abandonded ahead of its time in your opinion?