Perhaps this will clear things out for you:
intellectual property
n.
A product of the intellect that has commercial value, including copyrighted property such as literary or artistic works, and ideational property, such as patents, appellations of origin, business methods, and industrial processes.
Source: The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
intellectual property
(IP) The ownership of ideas and control over the tangible or virtual representation of those ideas. Use of another person's intellectual property may or may not involve royalty payments or permission, but should always include proper credit to the source.
(1997-03-27)
Source: The Free On-line Dictionary of Computing, © 1993-2001 Denis Howe
The law has made it legal for an emulator to make use of the original system's BIOS/ROM if it's running unchanged on the original hardware as that isn't infringing on the intellectual property. But an OS on the other hand, may not as it would be infringing on the intellectual property of the owners to the original OS.