No. The EULA for Mac OS X Lion Server says:
2 . Permitted License Uses and Restrictions.
A. Standard and Preinstalled Apple Software License. Subject to the terms and conditions of this License, unless you obtained the Apple Software from the Mac App Store or under a volume license, maintenance or other written agreement from Apple, you are granted a limited, non-exclusive license to install, use and run one (1) copy of the Apple Software on a single Apple-branded computer at any one time. For example, these standard, single-copy license terms apply to you if you obtained the Apple Software preinstalled on Apple- branded hardware.
which means you can't install it on non Apple-branded hardware (but it might be legal if you virtualize using Apple hardware on Windows)