It would have to be more than that. If it's supposed to be backed by EU there would have to be an agency responsible for it's development and security. The moniker "EU certified" would require some sort of code evaluation and certification agency. As such it would become rather powerful.
I think it's a good idea, the OS would give the market a focus and allow for a collected development effort without excluding anyone active today from participating. Kinda like what I think Android was, without the risk of lock-in as it would be government funded.
The big question is if this would be within the current EU mandate, though.
As I get it, it's about shifting the perspective from everything is for cars and pedestrians are an after thought to something like everything is for pedestrians except this particular piece of road where cars may drive. From "car first", to "pedestrian first".