Is TwistedBrush Pro Studio compatible with Windows 8.1?
Yes. Windows 8.1 may request permission to install the DirectPlay component. This is normal. Here is additional information on this.
If Windows is configured to not automatically install optional components an error may be reported as unable to start Win32DPNetGame. In this case you may need to manually enable the DirectPlay functionality of Windows.
Control panel -> Programs -> Programs and Features -> Turn windows features on or off