MacWorks Plus was a complete implementation (port) of the Macintosh Plus 128K ROM on the Apple Lisa and Macintosh XL computer systems,  a contract developer named Chuck Lukaszewski, who was responsible for versions up through 1.1(h), which supported up to which graphical user interface-based operating system for Macintosh computers, and was shipped with various Macintosh computers until it was succeeded by System 7 in 1991?
System 6 System 6 (also referred to as System Software 6) is a graphical user interface-based operating system for Macintosh computers. It was released in 1988 by Apple Computer and was part of the classic Mac OS line of operating systems. System 6 was shipped with various Macintosh computers until it was succeeded by System 7 in 1991. The boxed version of System 6 cost $49 when introduced. System 6 is classed as a monolithic operating system. It featured an improved MultiFinder, which allowed for co-operative multitasking.
Apple Computer Inc v Mackintosh Computers Ltd Apple Computer Inc v Mackintosh Computers Ltd [1990] 2 S.C.R. 209, is a Supreme Court of Canada case on copyright law regarding the copyrightability of software. The Court found that programs within ROM silicon chips (in this case, the Autostart ROM and Applesoft in Apple II+ systems) are protected under the Copyright Act, and that the conversion from the source code into object code was a reproduction that did not alter the copyright protection of the original work.