业内预计，未来2-3年内行业将出现When Linus reimplemented UNIX, writing the Linux kernel, the situation was somewhat more complicated, with an additional layer of indirection. He was exposed to UNIX just as a user, but, apparently, had no access to the source code of UNIX. On the other hand, he was massively exposed to the Minix source code (an implementation of UNIX, but using a microkernel), and to the book describing such implementation as well. But, in turn, when Tanenbaum wrote Minix, he did so after being massively exposed to the UNIX source code. So, SCO (during the IBM litigation) had a hard time trying to claim that Linux contained any protected expressions. Yet, when Linus used Minix as an inspiration, not only was he very familiar with something (Minix) implemented with knowledge of the UNIX code, but (more interestingly) the license of Minix was restrictive, it became open source only in 2000. Still, even in such a setup, Tanenbaum protested about the architecture (in the famous exchange), not about copyright infringement. So, we could reasonably assume Tanenbaum considered rewrites fair, even if Linus was exposed to Minix (and having himself followed a similar process when writing Minix).