Lumberyard source is now available on GitHub. You can check it out at www.github.com/aws/Lumberyard. Instead of using the installer, you can now access Lumberyard source code directly from GitHub and use GitHub to manage your code.

Another benefit: submit code changes back to Lumberyard.

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In the past, Lumberyard devs were only able to submit up to 50 lines of Lumberyard code through the forums, which limited fixes to simple changes. (Thanks again for all your submissions!) Now, with GitHub, there’s a simple way to submit changes and fixes of any size to the Lumberyard team. With pull requests, you can submit as much code as you want, across as many files as you want, knowing your changes will be managed in a concise and correct manner. Your feedback and support are what drives our team, and we’re excited to be able to build this engine alongside you.

Learn more at their announcement: https://aws.amazon.com/it/blogs/gamedev/now-available-lumberyard-on-github/.