Set up the project with your favorite IDE (Eclipse, Netbeans, etc.)

Eclipse

First, install gradle plugin :

Help / Eclipse marketplace / search "gradle" and install Gradle integration for Eclipe

Or https://marketplace.eclipse.org/content/gradle-integration-eclipse-44

Then :

• clone the repository as usual,
• import a Gradle project (File->Import...->Gradle->Gradle Project),
• browse to the cloned repository root directory,
• clic Build Model,
• select core project and you're done.

NetBeans / jMonkey SDK

First, install gradle plugin :

Tools / Plugins / Available plugins / search "gradle"

Or http://plugins.netbeans.org/plugin/44510/gradle-support

Then,

• clone de repository as usual (team->git->clone),
• ask to open existing project after cloning,
• it should ask you which project to open. Expand OpenRTS and select "core",
• wait for cloning and you're done.