Larry J. Blunk: Apologies if this has been answered before, but I noticed that there are AT&T copyright notices in the kernel sources for Unix Edition 5, but they were removed in Edition 6. [...] I noticed that USL registered Editions 5, 6, 7 and 32V in 1992. I would assume that Editions 4 and earlier are free and clear [...] As I understand it, Editions 7 and 32V could have had copyright protection without registration since they were released after 1978. However, because they lacked copyright notices when released, they may very well be considered public domain. It was not until 1989 that the requirement for including copyright notices was dropped. ======== Notwithstanding other comments about the history, for practical purposes none of this matters for Seventh Edition and 32V and anything earlier, because Caldera (as it then was) open-licensed them in January 2002; see http://www.tuhs.org/Archive/Caldera-license.pdf. To be precise, that license covers 32-bit 32V UNIX 16 bit UNIX Versions 1, 2, 3, 4, 5, 6, 7 with specific exclusion of System III and System V and successors. That is why source code for the Seventh Edition system (for example) is openly accessibly on the TUHS web server. Among those whose dog work produced first a hobbyist-specific per-person license, then the current BSD-like license, was Warren Toomey, who manages that web server and this mailing list. I don't think it will give him a swollen head (or a wooden leg) to thank him now and then, and I do so here. Long-time readers know all that, but those who have joined us recently might not. Norman Wilson Toronto ON