They can. It is just a matter of being protected. If it isn't licensed, the risk is that some other person or company can claim it as theirs and license it such that it is proprietary ie. trademarked.
My opinion, and I wouldn't take it for much is go with the MIT license and don't worry much. In a nutshell, it allows anyone to take it and do what they want with it and you won't have to worry about keeping it free or compatible with other open source license.
Sorry the license thing is kind of a drag when you just want to create.