Although fierce rivals in the market for cloud computing services, IBM and Microsoft have pledged to make their technologies interoperable in the cloud for the sake of their users.

On Wednesday, the companies jointly announced that many Microsoft enterprise products would run on IBM's infrastructure and platform services, and that many key IBM middleware products would be available for use on Microsoft Azure.

"The cloud is an interesting change in the technology landscape. In a lot of ways it opens everybody up to be your partner as well as your competitor, more so than on-premise software did in the past," said Michael Curry, IBM vice president of WebSphere product management. "The key element here is about offering choice for our customers -- to have the flexibility to deploy software in lots of different places."

IBM middleware such as WebSphere application server, the Websphere MQ messaging bus and the DB2 database will be made available on Microsoft's Azure cloud service, while Microsoft's Windows Server and SQL Server will be offered as part of the IBM Cloud set of infrastructure services, and the Microsoft .NET runtime will be offered on IBM's Bluemix platform service.

Customers will also be able to run in the IBM Cloud their virtual machines based in the Windows Server Hyper-V hypervisor. IBM's Pure Application Service, IBM's approach for packaging a set of applications to run in the cloud, will be available on Azure.

Both companies will also honor preexisting licenses for software use from the other company. Microsoft will also offer the ability to purchase IBM middleware software licenses on a pay-per-use basis on Azure.

Some of the fruits from this work will appear immediately. IBM SoftLayer already offers a wide range of Microsoft software, such as Windows Server and Hyper-V. Other projects, such as making a copy of .NET to run on Bluemix might take some time due to the engineering work that would be needed, Curry said.

"We want to attract .NET developers to understand the power of Bluemix to build a new class of cloud applications," Curry said.

Curry expected that a preview of the Bluemix-based .NET would be available within the next several months.

The two companies, which both appear to be catching up with Amazon's lead in offering cloud services, seem to be running pretty close in acquiring new customers.

IBM generated US$4.4 billion in cloud-related revenue in 2013, and this year sales have increased by an additional 50 percent, according to the company. In its latest fiscal quarter, ending in June, Microsoft reported an 147 percent increase in cloud revenue, which would bring its current annual run rate to about $4.4 billion as well, according to the company.

Joab Jackson covers enterprise software and general technology breaking news for The IDG News Service. Follow Joab on Twitter at @Joab_Jackson. Joab's e-mail address is Joab_Jackson@idg.com