The Apple II and IBM PC computer lines were "cloned" by other manufacturers who had reverse-engineered the minimal amount of firmware in the computers' ROM chips and subsequently legally produced computers that would run the same software. These clones were seen by Apple as a threat, as Apple II sales had presumably suffered from the competition provided by Franklin Computer Corporation and other clone manufacturers, both legal and illegal. At IBM, the threat proved to be real: most of the market eventually went to cloners like Compaq, Leading Edge, Tandy, Kaypro, Packard Bell, and dozens of smaller companies, and in short order IBM found it had lost control over its own platform.
Apple eventually licensed the Apple II ROMs to other companies. Apple licensed the Apple II ROMs to educational toy manufacturer Tiger Electronics to produce an inexpensive laptop with educational games and the AppleWorks software suite, the Tiger Learning Computer (TLC). The TLC lacked a built in display. Its lid acted as a holster for the cartridges that stored the bundled software since it had no floppy drive.
Wary of repeating history and wanting to retain tight control of its product, Apple's Macintosh strategy included technical and legal measures that rendered the production of Mac clones problematic. The original Macintosh system software was a very large amount of complex code that embodied the Mac's entire set of APIs, including the use of the GUI and file system. Through the 1980s and into the 1990s, much of the system software was included in the Macintosh's physical ROM chips. Therefore, any competitor attempting to create a Macintosh clone without infringing copyright would have to reverse-engineer the ROMs, which would have been an enormous and costly process without certainty of success. Only one company, Nutek, managed to produce "semi-Mac-compatible" computers in the early 1990s by partially re-implementing System 7 ROMs.
Before true clones were available, the Atari ST could be converted into a Mac by adding the third-party Spectre GCR emulator, which required that the user purchase a set of Mac ROMs sold as system upgrades to Macintosh users. The Amiga could also be converted into a Mac with similar emulators. Since Apple Computer never manufactured a 68060-based Mac, the fastest way to run native 68000 Mac OS applications without emulation is to run it on an Atari or Amiga with a 68060 upgrade.
There was also a software emulator for x86 platforms running DOS/Windows and Linux called Executor, from ARDI. ARDI reverse engineered the Mac ROM and built a 68000 CPU emulator, enabling Executor to run most (but not all) Macintosh software, from System 5 to System 7, with good speed. The migration from 68000 to PowerPC, and the added difficulties of emulating a PowerPC on x86 platforms, made targeting the later Mac OS versions impractical.
The first Macintosh clones 
Apple's strategy of suppressing clone development was successful. From 1986 to 1991, several manufacturers created Macintosh clones, including the portable Outbound; however, in order to do so legally, they had to obtain official ROMs by purchasing one of Apple's Macintosh computers, remove the required parts from the donor, and then install those parts in the clone's case. In 1986, Apple made a deal to sell discounted Macintosh computers to Dynamac for conversion. In 1988, Colby Systems, which had previously produced their Macintosh-compatible laptops on a trade-in basis, began selling them to Apple dealers who would then fit motherboards from their spare stock.
In the 1980s, Brazil's military dictatorship instituted trade restrictions that prohibited the importation of computers from overseas manufacturers. A Brazilian company called Unitron (which had previously produced Apple II clones) developed a Macintosh clone with specifications similar to the Mac 512K, and proposed to put it on sale. Although Unitron claimed to have legitimately reverse-engineered the ROMs and hardware, and Apple did not hold patents covering the computer in Brazil, Apple claimed the ROMs had simply been copied. Ultimately, under pressure from the US government and local manufacturers of PC clones the Brazilian Computer and Automation Council did not allow production to proceed.
Official Macintosh clone program 
By 1995, Apple Macintosh computers accounted for around 7% of the worldwide desktop computer market. Apple executives decided to launch an official clone program in order to expand Macintosh market penetration. Apple's clone program entailed the licensing of the Macintosh ROMs and system software to other manufacturers, each of which agreed to pay a flat fee for a license, and a royalty (initially $50) for each clone computer they sold. This generated quick revenues for Apple during a time of financial crisis. From early 1995 through mid-1997, it was possible to buy PowerPC-based clone computers running Mac OS, most notably from Power Computing. Other licensees were Motorola, Radius, APS Technologies, DayStar Digital, UMAX, MaxxBoxx, and Tatung. However, by 1996 Apple executives were worried that high-end clones were cannibalizing sales of their own high-end computers, where profit margins were highest.
Jobs ends the official program 
Soon after Steve Jobs returned to Apple in 1997, he backed out of recently renegotiated licensing deals with OS licensees that Apple executives complained were still financially unfavorable. Because the clone makers' licenses were valid only for Apple's System 7 operating system, Apple's release of Mac OS 8 left the clone manufacturers without the ability to ship a current Mac OS version and effectively ended the cloning program. Apple bought Power Computing's Mac clone business for $100 million, ending the Clone era. Only UMAX ever obtained a license to ship OS 8, which expired in July 1998.
Jobs publicly stated that the program was ill-conceived and had been a result of "institutional guilt," meaning that for years, there had been a widely held belief at Apple that had the company aggressively pursued a legal cloning program early in the history of the Macintosh, consumers might have turned to low-priced Macintosh clones rather than low-priced IBM/PC-compatible computers. Had it pursued a clone program in the 1980s, in this view, Apple might have ended up in the position that at the time was occupied by Microsoft – an extremely powerful company with high profit margins and a wide base of consumers perpetually dependent on its system software products. Jobs claimed it was now too late for this to happen, that the Mac clone program was doomed to failure from the start, and since Apple made money primarily by selling computer hardware, it ought not engage in a licensing program that would reduce its hardware sales.
In 1999, Jobs did have discussions with Ben Rosen, Chairman and interim CEO of Compaq at the time, for the world's then-largest Wintel PC manufacturer to license Mac OS which would have been a coup for Apple. However no agreement was reached, as Apple had second thoughts about licensing its "crown jewel", while Compaq did not want to offend Microsoft whom they had partnered with since their founding in 1982. By 2007, Rosen told Jobs he had switched to being a Mac user.
Later Macintosh cloning 
Since Apple transitioned the Macintosh to an Intel platform in 2006, and subsequent to a major increase in visibility and a gain in computer market share for Apple with the success of the iPod, large computer system manufacturers such as Dell have expressed renewed interest in creating Macintosh clones. While various industry executives, notably Michael Dell, have stated publicly that they would like to sell Macintosh-compatible computers, Apple VP Phil Schiller said the company does not plan to let people run Mac OS X on other computer makers' hardware. "We will not allow running Mac OS X on anything other than an Apple Mac," he said.
From around 2007 to 2009, a company called Psystar attempted to sell what they thought were legal clone machines. But a protracted legal challenge followed, as Apple brought a lawsuit against them under the DMCA, a point US District Court Judge William Alsup agreed with Apple on, and therefore found against Psystar who then halted sales altogether of their Mac clone machines.
The Hackintosh approach 
Hackintosh is the term appropriated by hobbyist programmers, who have collaborated on the Internet to modify versions of Mac OS X v10.4 onwards —dubbed Mac OSx86— to be used on generic PC hardware rather than on Apple's own hardware. Apple still contends this is still illegal under the DMCA, so in order to combat illegal usage of their operating system software, they continue to use methods to prevent Mac OS X from being installed on unofficial non-Apple hardware, with mixed success.
- Coventry, Joshua (2006-12-05). "Apples From Other Orchards". Low End Mac. Retrieved 2007-03-04.
- Owad, Tom (2004-01-19). "Bell & Howell Apple II+". Applefritter. Retrieved 2007-03-04.
- "MacOS-Compatible Systems: NuTek". EveryMac.com. Retrieved 2006-05-25.
- "The Official ShapeShifter Home Page".
- Eric Taub (1991), "Taking your Mac on the road: Outbound Laptop System - Hardware Review - alternative to Apple Macintosh Portable from Outbound Systems Inc - evaluation", Home Office Computing
- O'Connor, Rory J. (24 November 1986), "Apple Backs Portable Mac By Dynamac- First Mac Laptop To Gain Approval", InfoWorld: 5
- Flynn, Laurie (31 October 1988), "Colby to Sell SE Model of Walk-Mac- Plans for Authorized Apple Dealers to Install Spare Motherboards", InfoWorld: 8
- "A Contraband Mac 512K". low end mac. Retrieved 2011-05-22.
- da Costa Marques, Ivan (2003), "O caso Unitron e condições de inovação tecnológica no Brasil", Proceedings of the 5th Brazilian Congress of Economic History and the 6th International Conference on Business History (in Portuguese) (Brazilian Economic History Society), archived from the original on 2004-12-08
- Linzmayer, Owen W. (2004-01-01). Apple Confidential 2.0: The Definitive History of the World's Most Colorful Company. pp. 254–256. ISBN 1-59327-010-0.
- Gruman, Galen (November 1997). "Why Apple Pulled the Plug". Macworld 14 (11). pp. 31–36
- Beale, Steven (October 1997). "Mac OS 8 Ships with No License Deal". Macworld 14 (10). pp. 34–36
- Beale, Steven (November 1997). "Apple Eliminates the Top Clone Vendor". Macworld 14 (11). pp. 30–31
- "Jobs reportedly wanted Compaq to license Mac OS". CNET.
- "Dell: We Would License Mac OS". betanews.com. Retrieved 2010-11-16.
- "Apple throws the switch, aligns with Intel". CNET. Retrieved 2005-06-06.
- Elmer-DeWitt, Philip (2009-11-14). "Apple wins clone suit". CNN Money. Retrieved November 15, 2009.
- Keizer, Greg (2009-11-15). "Apple Wins Court Victory Over Mac Clone Maker Psystar". PC World. Retrieved November 15, 2009.
- Keizer, Gregg (November 30, 2008). "Apple adds DMCA charge to lawsuit against Psystar: It accuses clone maker of breaking Mac OS copy-protection scheme". computerworld.com. Retrieved 2009-12-20.