I'm creating a project on codeplex that uses Amazon Web Services and the AWS SDK for .NET Which licenses can I use? The SDK is released under Apache 2.0 license, so I assume my project can or should use the same. If I add another open source library released under a different license, do I need to find a license that is 'compatible' with both ie. one that has the same requirements for derivative works? My requirement is for a license that allows me to publish a derivative work from the AWS .NET SDK. I can use any of the licenses that codeplex supports, which includes: Apache 2.0 GNU GPLv2 MIT Mozilla Public License 2.0 Microsoft Public License