1. Install Motion Builder.
2. Run the FlexLM license tool and write down your FlexLM hostid (Ethernet Mac Address).
You can also get it by opening a shell and type : ipconfig /all
3. Open the license file aw.dat and replace "your_host" by your FlexLM hostid.
4. Drag and drop the license file on awkeygen.exe.
5. Create a flexlm dir on the root of your c: drive and copy the license there.
If you already have such license for Maya or Mudbox you can use notepad to
merge the license files.
6. Enjoy it!