The core package is, since version 4 in December 2010, free software under GNU General Public License version 2 (GPLv2). The separate "VirtualBox Oracle VM VirtualBox extension pack" providing support for USB 2.0 and 3.0 devices, Remote Desktop Protocol (RDP), disk encryption, NVMe and Preboot Execution Environment (PXE) boot is under a proprietary license, called "Personal Use and Evaluation License (PUEL)", which permits use of the software for personal use, educational use, or evaluation, free of charge. Since VirtualBox version 5.1.30 Oracle defines personal use as the installation of the software on a single host computer for non-commercial purposes.