It is responsibility of the entity (Microsoft in this case) publishing the code to make sure that they have the right to publish. The Linux kernel generally requires non anonymous contributions for that reason. As a guarantee that the person has the right to contribute.
> It is responsibility of the entity (Microsoft in this case) publishing the code to make sure that they have the right to publish.
This would basically kill github as an idea. I like the ability to be able to push some personal project to github and don't really give a fuck about technical copyright violations and I think the same is true for 90% of developers.
