The term implies that the design team works in an environment that is "clean" or demonstrably uncontaminated by any knowledge of the proprietary techniques used by the competitor.
The previous PC "clone" examples are notable for not daring to fight IBM in court, even before the legal precedent for copyrighting firmware had been made.
[14] In the early years of its existence, Coherent's developer Mark Williams Company received a visit from an AT&T delegation looking to determine whether MWC was infringing on AT&T Unix property.
From this evidence, the judge concluded that similarity in certain routines was a matter of functional constraints resulting from the compatibility requirements, and thus were likely free of a creative element.
A related aspect worth mentioning here is that NEC did have a license for Intel's patents governing the 8086 processor.
[17] Sony Computer Entertainment, Inc. v. Connectix Corp. was a 1999 lawsuit which established an important precedent in regard to reverse engineering.
Connectix's successful appeal maintained that the direct disassembly and observation of proprietary code was necessary because there was no other way to determine its behavior.