I would recommend to double check those links to the github orgs, I’m sorry to say they are small projects. Can’t compare with publishing the whole frontend, their image managing library and their text editor.
The NYT has 65 projects, most of which have a few hundred stars, and many in the thousands.
It's lower for some of the others. But it still seems to me that these publishers default to publishing their code.
BUT: most publishers probably do not run an entirely home-grown system. Indeed, you will find many Wordpress plugins or rails gems among those published projects. And for the homespun solutions, it's likely that they are too specific to a publisher to be usefully open-sourced without a major investment of resources, like the Guardian's undertaking.
It's lower for some of the others. But it still seems to me that these publishers default to publishing their code.
BUT: most publishers probably do not run an entirely home-grown system. Indeed, you will find many Wordpress plugins or rails gems among those published projects. And for the homespun solutions, it's likely that they are too specific to a publisher to be usefully open-sourced without a major investment of resources, like the Guardian's undertaking.