Red Hat announces they will distribute an OpenJDK for Windows platform: http://developers.redhat.com/blog/2016/06/27/openjdk-now-available-for-windows/
EDITED (thx to CaseyB comment): there is no PRODUCTION support on Windows. From the documentation:
All Red Hat distributions of OpenJDK 8 on Windows are supported for development of applications that work in conjunction with JBoss Middleware, so that you have the convenience and confidence to develop and test in Windows or Linux-based environments and deploy your solution to a 100% compatible, fully supported, OpenJDK 8 on Red Hat Enterprise Linux.