The new pricing scheme will let application providers who offer their software as a service pay for IBM software, including WebSphere Application Server and IBM DB2, on a monthly basis as they use it.

"What they've said to us on many occasions is, 'well, IBM, can't you charge me for the middleware in line with how I get paid for my solution?'" said Dave Mitchell, director of strategy for IBM's software business partners. Software-as-a-service providers typically charge customers only for what they use.

Mitchell compares the new monthly rental structure to mobile-phone subscriptions, where users sign up for a contract, committing to a certain usage level per month and agreeing to pay for additional use above that level. As with mobile-phone subscriptions, in IBM's monthly rental model, the more a customer commits to, the bigger the discount on the fee.

Also, IBM has chosen 20 of its most popular products and will let its customers mix and match the use of them in order to meet their monthly revenue commitment. For example, if a customer signs up to pay for US$10,000 worth of software, the customer can use $7,000 worth of WebSphere and $3,000 worth of DB2, or any other combination that adds up to $10,000.

Without the new monthly rental structure, customers must buy an IBM license to use the software based on the maximum estimated amount of usage, even if the software is used less some of the time. They may also have to pay for the whole license up front. If they estimate usage too low, adding more users may be expensive and a hassle. Under the monthly rental model, adding users would be less costly.