Evolution
The most widely deployed UNIX operating systems using the POSIX standards, or Single UNIX Specifications, are the SYSV descendants.
SYSV Descendents
| OS | Description |
|---|---|
| Solaris | (developed by Sun Microsystems and now owned by Oracle) |
| AIX | (owned by IBM), |
| HP-UX | (owned by Hewlett Packard). |
| MAC OS X | Apple uses the POSIXstandards - though at its core Apple’s OS is based on BSD |
Unix-Like
| OS | Desc |
|---|---|
| Linux | Developed by Linus Torvalds |
| FreeBSD | BSD Variant |
| NetBSD | BSD Variant |
| OpenBSD | BSD Variant |
Trademark
It is also important to note the term UNIX is trademarked by The Open Group. To use the UNIX trademark, along with ensuring a product meets the “Single UNIX Specification” (the successor of POSIX) - a collection of specification documents that are part of the X/Open Common Application Environment (CAE) - vendors must pay a licensing fee to brand their products. Those variants that use POSIX, or the Single UNIX Specification, but are not licensed by The Open Group, are generally considered to be systems that behave like UNIX, but are not true UNIX. Again, these variants are commonly referred to as UNIX-like systems.