It's a great start.
Nobody is open to just anyone modifying their code, whether Open Source or proprietary.
Random people from the internet cannot have their code accepted into the Linux kernel, Firefox, GNU, Java, Ruby, or any other popular Open Source project. They do not have commit access, and the people that can commit code vet contributions quite extensively.
The only group who suggests otherwise is Microsoft - I'm surprised your comment has been moderated up.
Jkush: "Right, I don't think Microsoft is open (pun intended) to just anyone modifying their baseline code. "
Clearly Microsoft wouldn't mind at all if someone modified the code for their personal use, as it wouldn't affect MS - the user would have an obviously unofficial version of whatever.
It seems the parent poster is implying that 'just anyone' could modify the actual mainline source code of an Open Source app. This is consistent with past statements from Microsoft about Open Source, usually along the line of "anyone can add code, you don't know where it comes from". Both are incorrect.