What is the open-source standard for packaging and distributing software applications for virtual machines?

The open-source standard for packaging and distributing software applications for virtual machines is specifically the Open Virtualization Format (OVF). OVF is designed to facilitate the deployment of virtual machines by providing a common format across different virtualization platforms. This helps ensure that virtual appliances can be easily shared and deployed, regardless of the underlying infrastructure.

OVF packages contain metadata that describes the virtual machine contents (like CPU, memory requirements, and virtual disks) in a standardized manner. This standardization is crucial for improving compatibility and ease of use when transferring virtual machines between different environments or virtualization solutions.

The other options, while related to virtualization, do not serve the same purpose as OVF. An OVA is essentially a single-file archive of an OVF package, which makes it convenient for distribution but is not the standard itself. VMDK refers to a specific disk image format used by VMware, containing disk data for virtual machines, while IMG is a generic file extension used for disk images and can contain various types of data but does not pertain specifically to virtual machine packaging standards.