You can use their data and (fast?) order fulfilment to test your algo to the point where you know it performs well, and then go off and do whatever wherever you want with it. You wouldn't "hand it over".
From Quantopian's FAQ: [1]
Q: Who owns my algorithms?
A: You own your algorithms. Everything you write is yours. Quantopian does not own your algorithms; you do.
Q: Are my algorithms secret?
A: Your algorithms are kept secret. We are committed to protecting your intellectual property and keeping it safe. Ideas are some of the most valuable assets anyone has. We take this responsibility to our members extremely seriously
Caveat: In their detailed terms: "If in the course of providing technical support or other maintenance of the Services it becomes necessary for Quantopian to view your private Content, such viewing will be restricted to the very specific technical purpose." [2]