I recall being in a similar situation. I had done significant marketing/PR for my project and that helped me avoid this issue. Since mine was an original project (a rare phenomenon), it was not very difficult to get the project famous amongst other students and then the professors.
The students in the next semester started asking me for the project files to copy it for submission as their own project. I had to be very polite to not give while maintaining my relationship with them.
This was a hardware project (IC design) I did back in 1998. Open source hardware was uncommon then, and most of the professors were not even online. Further, open-sourcing this would have meant more students in the upcoming semesters copying the work and submitting it as their own, something which I did not want.
The students in the next semester started asking me for the project files to copy it for submission as their own project. I had to be very polite to not give while maintaining my relationship with them.