看了下lz原来的repo，你没有加入license信息，所以默认是按版权法规定all rights reserved。
但同时你注册的时候又表明同意GitHub的服务条款，所以其他人有查看、fork你的代码的权利。
如果是有license的情况下，楼上说的别人把你的repo拷贝了，然后建了一个新repo的行为，在没有违反license的情况下，是没有任何问题的。
开源不是简单的贴代码，没license并不算开源。
来源：
https://help.github.com/articles/open-source-licensing#what-happens-if-i-dont-choose-a-licenseWhat happens if I don't choose a license?
You're under no obligation to choose a license. It's your right not to include one with your code or project, but please be aware of the implications. Generally speaking, the absence of a license means that the default copyright laws apply. This means that you retain all rights to your source code and that nobody else may reproduce, distribute, or create derivative works from your work. This might not be what you intend.
Even if this is what you intend, if you publish your source code in a public repository on GitHub, you have accepted the Terms of Service which do allow other GitHub users some rights. Specifically, you allow others to view and fork your repository.
If you want to share your work with others, we strongly encourage you to include an open source license.