CentOS
CentOS as a group is a community of open source contributors and users which started in 2003 and has been sponsored by Red Hat since 2014. CentOS Linux versions up to CentOS Linux 8 are 100% compatible rebuilds of Red Hat Enterprise Linux, in full compliance with Red Hat's redistribution requirements.
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FreeBSD
FreeBSD is a UNIX-like operating system for the i386, amd64, IA-64, arm, MIPS, powerpc, ppc64, PC-98 and UltraSPARC platforms based on U.C. Berkeley's "4.4BSD-Lite" release, with some "4.4BSD-Lite2" enhancements.