According to the license agreement for the server version of its new Leopard OS, users can install on Apple computers "other copies of Mac OS X Server software" in addition to the original copy, provided that all the additional copies are fully licensed.

Under those terms, users could partition their Apple servers into multiple, virtual machines using virtualization software from vendors like Parallels and others.

Virtualization lets users discretely run multiple instances of an OS on a single machine. In addition to boosting capacity utilization, the technique can be used to enhance security by separating workloads that require different levels of protection.

Until now, Apple did not allow users to run multiple copies of its operating system on a single server. However, there are signs that the computer maker is gearing more of its technologies and policies toward business users in an effort to make inroads against Microsoft in corporate computing environments.

The client version of Leopard, released on October 26, contains numerous enhancements aimed at corporate users.

Because it's Unix-based, Leopard offers a number of features that could appeal to business IT managers. Among other things, Leopard is compliant with POSIX (Portable Operating System Interface), a standard designed to ensure that code authored for one POSIX system will work on another.

Leopard also provides a Terminal application that advanced users can employ to access the operating system's underlying Unix interface. The software will also natively run 64-bit or 32-bit applications.

Beyond its Unix credentials, Leopard comes with a preinstalled version of Bootcamp -- software that allows users to boot Windows on a Macintosh. That could help Apple overcome the dearth of business applications currently available for the Mac OS.

Still, Apple has a long way to go if it's to make a splash in the business computing market. Various estimates put the company's overall share of the PC market at between 5% and 6%, but the number drops considerably in corporate environments -- where Macs are usually confined to art and graphics departments.

Microsoft aside, Leopard also has to compete with Linux -- a Unix-like open source operating system -- for a larger share of the corporate market. Linux commands more than 12% of the server market, according to researchers at IDC, though it controls only a miniscule portion the desktop market.