Yes, BlueJ is compatible with Windows 8.1. In fact, the developer mentioned on its official website that the environment is compatible with Windows 2000, XP, Vista or newer. This means you have the possibility to install the application along with JDK in Windows 7, Windows 8, Windows 8.1, and Windows 10.
Downloads page: http://www.bluej.org/versions.html
Note: You have the possibility of downloading only the application. This applies only when you already have JDK installed and running.