Petitions have weight providing they're coming from the right places. There's a difference between the random internet petitions that random users make, and petitions coming from bodies such as unions or regulatory bodies.
This is a petition being put forward from a well known organisation, so I would gather it actually has some weight.
Yes - but the vast majority of people are not going to be downloading forks or modified versions of software, they will always get it directly from the source.
The "default", so to speak, has a lot of power.