[citation][nom]B-Unit[/nom]IBM isn't licenced to produce chips featuring the x86 instruction set, only Intel, AMD and VIA are.[/citation]
Well actually it's Intel the proprietary of the x86 patents. So it's Intel that licenses it to AMD and VIA.
Anyway there are three aspects to consider:
1) Intel sells x86 processors to IBM (and so does AMD) but sells also to Dell, HP, Siemens, Apple, ... , and so probably for the Windows Server market it's cheaper for IBM and other companies to buy the chips to Intel rather than to produce them and pay royalties to Intel. And IBM is also one of the most important customers for Intel and Intel don't want IBM to focus only on AMD x86, POWER and Cell processors... you'll never know what Intel could expect from that important change.
2) IBM had an important experience several years ago with Cyrix processors which was a fiasco. So probably it's not interesting to go back in time and do it again.
3) It is known that IBM pushes AMD, providing technology and know-how (just like that High-K stuff), and AMD is a special case regarding in using Intel x86 patents (just read the recent news about Intel+AMD agreement for 5 years!).
So this is a long term complex relationship between Intel and IBM regarding x86, because both are producers, sellers and customers!