Bochs (box) is a portable IA-32 and x86-64 IBM PC compatible emulator and debugger mostly written in C++ and distributed as free software under the GNU Lesser General Public License. Developed by http://bochs.sourceforge.net/
License: Open Source
Portable VirtualBox is a user-friendly virtualization tool that supports a wide range of guest operating systems with good performance and features like USB support and snapshots, making it ideal for casual users. In contrast, Bochs is a more complex, open-source emulator that offers deep customization and the ability to emulate legacy systems, but it has a steeper learning curve and less performance compared to Portable VirtualBox.