Well, you are correct. It is possible to "migrate" in some cases, but IBM makes it very difficult. I have some contact with those who work with IBM sales reps... and they are pretty awful. Just the mere threat of legal action changes plays on the low risk aversion of customers in the high-end, no downtime space. IBM's sales reps are FUD machines. However, from what I understand, the actions aren't limited to migration options... although I imagine that is what scares them the most (and I am not just talking about full migration... b/c IBM charges by the MIP/amount processed by the mainframe processor and charges less for non-locked in customers [by a factor of 10 sometimes] there is a huge $$ savings to be realized by even offloading some processing. Ashlee Vance's Blog article on NYT was very interesting... featured a company called Neon.Check out this snippet from the article.

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Add Neon Enterprise Software to the list of companies complaining about I.B.M.’s practices in the mainframe market. Neon makes software and related technology than can offload certain tasks onto specialized chips inside mainframes. This tactic can save customers a lot of money because I.B.M. charges for its mainframes based on the amount of computing horsepower and software a company consumes. So, if you send some of the heavy lifting over to specialized chips that can crank away on the jobs at a very quick rate, then you can reduce your overall mainframe costs, Lacy Edwards, the chief executive of Neon said. “We discovered that if you launch big jobs on the specialty processors, you could save millions of dollars per year,” Mr. Edwards said. “And the more work you move over, the cheaper it becomes.” The specialty chips in question are made by I.B.M., just like the regular mainframe chips. Historically, the specialized chips have been cheaper and do not come with the same usage or software costs associated with the main chips. The challenge has been in tweaking software to direct certain jobs to the cheaper silicon. Neon’s engineers solved this problem with a product the company calls zPrime that sends things like database and transaction processing jobs to the specialized chips. According to Mr. Edwards, Neon hired a team of lawyers to make sure the company’s approach did not violate I.B.M.’s intellectual property or licensing arrangements. About 100 customers have started testing zPrime since it went on sale about three months ago, Mr. Edwards said. “A lot of the savings these customers are getting would come out of I.B.M.’s pocket,” Mr. Edwards said. And Big Blue is none too happy about it. “Over the past few weeks, I.B.M. has started refusing to sell customers additional specialty processors unless they agree to some new restrictions, which would make it a violation of their customer agreements if they use them for zPrime,” he said. A number of smaller companies have groused about similar tactics used by I.B.M. in recent years to bolster its mainframe business. "

This is not necessarily the case. Although it is correct to say that usually a company is under no "duty" to license out its IP, there are notable exceptions. One being, if a company has licensed its IP openly in the past and made assurances of future RAND licensing and a market/ecosystem has formed around it and then when it reaches a dominant position where the entry barriers are high (i.e. "installed base opportunism") and changes it strategy in order to make exorbitant profits--then antitrust might recognize a duty to deal.

In the mainframe space, IBM was under a consent decree (settlement with government) and government scrutiny until 2001, where it was deemed that due to changes in the IT world - the decree was no longer necessary b/c IBM faced new sources of competition. This competition never materialized--and in fact the few competitors who were in the market exited because they were no longer guaranteed interface specifications and licensing necessary to make compatible machines.

From the customer side, the vast majority of the world's corporate and public sector data is locked-into the mainframe--especially areas that require high-levels of batch processing--financial institutions, airlines, credit card companies, health care, social security administration, etc. It is incredibly hard to "migrate" off of a mainframe--sometimes impossible. This is why IBM can charge so much to legacy users--a gig of RAM on a mainframe costs almost $6,000--a little bit of a markup. In fact, mainframes apparently account for nearly a 1/4 of IBM's nearly $100 million annual revenue. The world is so tied to mainframes behind the scenes--IBM has even said on its own website: "It is no exaggeration to say that, without the Internet, many businesses would suffer but, without the IBM mainframe, the global financial system would collapse."

The companies at which IBM has allegedly taken this action against have all focused on helping customers migrate off the mainframe and allow this data to move to other, less expensive machines. It would definitely make business sense for IBM to do that--however, I also believe it is a likely violation of antitrust law--both here and in Europe.