Software licenses, regardless of whether they are intended for open source or commercial projects, are designed to protect the intellectual property of the owner. Even though your apps are developed using Open Source principles, they nonetheless have value and it's in your best interest to take the minimum steps necessary to protect the efforts of your (and your team's) labor.
Choose a License is one resource that can help you evaluate the differences between the various open source licenses so you can make an informed decision.
Comparison of Free and Open-source Software Licenses OpenSource.org