You are expected to act ethically. See the The JHU Ethics site for more details on the university's ethics policy, and also read the CS Department's academic integrity code.

Course Cheating Policy

Project Cheating Policy

Since the course project is open-ended, it is easy to "re-use" knowledge that you may already have, or to re-use other code you may find on the web or obtain through others. Any such instance of re-use will most of the time be OK but must be documented in your submitted documents. Examples include: writing a Java version of a project you did last summer in C++; writing a rip-off of a PC application you know well; using a project idea that a group (of who a friend/relative of yours was a member) had developed previously in this course or some other course or job. Rip-offs are great, as long as you acknowledge your sources. If in doubt about whether an instance of re-use should be documented, e-mail or talk to the professor. Reuse of code which is not so acknowledged is considered cheating.