Incorrect. He created a POSIX-compliant kernel based on the Minix (a student-oriented teaching kernel) kernel. The only thing Linux and UNIX have in common is POSIX-compliancy.
IBM Jumps on Open-Source Bandwagon with Patent Promise
August 5, 2004
IBM announced that it will not use its patents against Linux, and it encouraged other software companies to make the same vow.
As the owner of 60 patents on which the Linux core might infringe, IBM could wreak havoc on Linux if it chose to do so.