The WiX toolset copyright is held by the .NET Foundation. Before we can accept any contributions you must have a Contribution License Agreement on file with the .NET Foundation. Fortunately the process is very easy. Just follow these steps:
If you don't have a GitHub account, create one.
Go here to authorize the .NET Foundation to access your GitHub account information.
Complete the Contribution License Agreement form and electronically sign the document.
While this process is underway you can participate in design discussions and actually write code. However, your code cannot be merged into the WiX toolset until the contribution license agreement is in place.