As for linux, it is an open source system that imitates the unix architecture and tries to be compatible with unix without reference to the unix code at all. In other words, bsd is a fork of Unix, and linux is a Unix-like system or a Unix-like system.
UNIX and Unix-like operating systems
| UNIX System V family |
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| BSD UNIX-386BSD family |
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| UNIX-Like |
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| other |
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