I took it from github https://github.com/msg768/mysteemit and modified UI and backend. There was no sign of copyright on Github page.
According to Github license I am allowed to do that. You can read it here
Number 5. License Grant to Other Users
Any Content you post publicly, including issues, comments, and contributions to other Users' repositories, may be viewed by others. By setting your repositories to be viewed publicly, you agree to allow others to view and "fork" your repositories (this means that others may make their own copies of your Content in repositories they control).