WinPE 3 входит в Windows Installation Automation Kit (WAIK). В лицензии на WAIK 7 записано:
You may not
...
• make more copies of the software than specified in this agreement or allowed by applicable law, despite this limitation;
• publish the software for others to copy;
• rent, lease or lend the software;
• transfer the software or this agreement to any third party;
...
Windows Pre-Installation Environment. You may install and use the Windows Pre-Installation Environment for purposes of diagnosing and recovering Windows operating system software. For the avoidance of doubt, you may not use the Windows Pre-Installation Environment for any other purpose, including without limitation as a general operating system, as a thin client or as a remote desktop client.”
То есть, единственным лицензионным использованием WinPE 3 будет диагностика и восстановление Windows. Любое другое использование не разрешено.
Eula для WADK 8 (WinPE 4) с ходу не нашёл, но скорее всего там аналогичное содержание.