Microsoft is warning customers that signing long-term enterprise license agreements can chain them for years to the unpredictable, often self-serving development schedule of an IT vendor\u2014which may not suit the customer's unique needs and priorities.\nYes, that Microsoft. \nIn a letter published Tuesday morning as a full-page ad in USAToday, Microsoft server-business chief Brad Anderson warned VMware customers\u2014just in time for the start of the VMworld conference\u2014that VMware would pressure IT shops to lock into VMware's approach to both virtual servers and cloud computing. \n"Signing up for a 3-year virtualization commitment may lock you into a vendor that cannot provide you with the breadth of technology, exibility or scale that you'll need to build a complete cloud computing environment," the letter reads, in part. \nAt VMworld Tuesday, VMware announced the latest version of its plans for VMware vCloud Director, a management product designed to give customers and service providers long-distance control and automation of hundreds or thousands of VMware virtual servers and clusters connected into cloud-computing structures. [ What's cool at this week's VMworld 2010 conference? See The Hottest Virtualization Products at VMworld. ]VMware's technology strategy is comprehensive and long-term, which means not only is not all of it shipping now, but also key parts\u2014including the vCloud cloud-management and automation platform\u2014won't be available until late this year or even next, according to James Staten, virtualization and cloud-computing analyst for Forrester. \nPressuring customers into long-term contracts commits them to a vision of cloud computing that's based on virtualizing servers within a data center using products from VMware, rather than identifying computing platforms and resources on a "pure cloud" basis, according to David Greschler, director of integrated virtualization strategy at Microsoft. \nBy contrast, Microsoft offers "a global-scale public cloud and online services" from its Azure platform-as-a-service offering, SaaS versions of SQL Server, Exchange and Sharepoint and virtualization products that compete directly with VMware, Greschler says. "What's really important to Microsoft is to communicate to customers that when we say 'cloud' we mean something much different and broader than when VMware says it," he says.Microsoft Cloud Offerings are Slow to Appear"Microsoft pressuring people to not sign enterprise license agreements or avoid lock-in is pretty rich," counters Bernard Golden, CEO of cloud computing consultancy Hyperstratus and a CIO.com blogger. "Microsoft does that all the time, including lock-in. If you're talking about that, with Azure, Microsoft is the only one offering it, so that's lock in. VMware clouds you can get from Terremark or Verizon or who knows how many other service providers. So that's a little disingenuous." \nDisingenuous, maybe, but not entirely inaccurate, Staten says. \n"Microsoft at least is grounded in that everything you're looking for in cloud computing from them they're delivering today and have been for a year," Staten says. "If you want to call your virtual environment your cloud, then VMware has a more robust solution that Microsoft currently does; if you're going to put something straight on a public cloud, you're more likely to do it with Microsoft than VMware." \nAzure , which Greschler and the USAToday letter both took pains to point out supports software built on Java, Ruby on Rails, PHP and Eclipse in addition to Microsoft's proprietary .NET, is a more friendly environment for developers wanting to build relatively simple applications without having to master the intricacies of virtualization at the same time, Staten says. \nAt the same time, Microsoft hasn't fulfilled all its promises of making its technology available through the cloud, Staten says. The company announced in 2008 that it would make all or most of its products available on cloud or SaaS basis, and change licensing to support subscription or other non-standard approaches. \nIt has made licenses more flexible to accommodate virtual servers, but has made far less progress toward SaaS-ification than expected Staten says, since the announcement was made at the July 2008 worldwide Microsoft partner conference, where Microsoft referred to it as "Software Plus Services." \nMicrosoft warning customers about enterprise licensing is pretty silly as well, Golden says. \n"This is all about who's going to be the big dog in this market," Golden says. "Both of them want to own the bottom, most fundamental portion of the architecture because a whole range of decisions flow from that one. Microsoft has done an incredible job of owning that in other areas and doesn't want to get displaced." \n\n Follow everything from CIO.com on Twitter @CIOonline.