Among the trends in today's enterprises is grid computing - an installation that taps the computing power of a large number of PCs or servers to run compute-intensive applications. Yet many grid computing users are finding that the key challenge they're facing isn't implementing the technology but figuring out how to pay for it.

Software licensing contracts, especially those with small software vendors, are generally unsuited to grid environments, which can quickly scale up or down depending on demand, said users at the recent Grid Today 2004 conference.

"One of the biggest problems of the grid is accounting," said John Hurley, director of grid evaluation and implementation at Boeing. "How do you pay for things? How do you set charges?" Hurley said he believes that software vendors are starting to address grid licensing issues, but it will take time to resolve them. The grid environment "is new for them also", he noted.

If a software licence is based on CPU usage, for example, costs can quickly escalate as more processors are called into service in a grid. Software vendors "cannot license their software around a true on-demand compute model," said Chris Bennett, group leader at Acxiom, a data integration company that uses grid technology both to manage resources across 4,000 mostly commodity-based servers, and to gain processing speed. Acxiom processes about 45 billion records each month.

"Can we get out from under software vendors' powers?" Bennett asked. "Can we make a truly scalable infrastructure where we are not at the whim of a software vendor?" Bennett said that most of the software on Acxiom's grid is either applications built in-house or open-source software. The company has about 300 developers.

While grid computing is gradually expanding into the mainstream enterprise, it's still mostly used for technical, compute-intensive applications, conference attendees said. And since smaller niche vendors often write applications for these systems, it's not unusual for licensing issues to arise.

"Because the vendors that we work with are small, it's very difficult to convince them that they should change their licensing practices," said Jeffrey Mathers, director of the research and innovation group at Johnson & Johnson Pharmaceutical Research & Development.

While large vendors such as IBM and Sun are developing licensing models that can be adapted to the grid environment, others are only beginning to come to terms with grid licensing. Albert Bunshaft, IBM's vice president of grid computing sales and business development, said grid licensing is an "unresolved problem." But he said he's seeing a lot of interest among applications vendors to work with IBM and users to adopt flexible terms.

Shahin Khan, vice president of Sun's high-performance technical computing business unit, said grid software licensing is "all over the map." But Sun's per-employee licensing adapts well to a grid environment, Kahn said.

IDC analyst Dan Kusnetzky said software vendors will have to adapt to the grid environment or risk losing users to open-source. "It's clear that licensing and business rules are going to have to be much more flexible" to deal with dynamic environments, he said.

However, some users say grid computing is worth whatever licensing problems companies may face. Mathers noted that when Johnson & Johnson was studying molecules used in drug development using computer simulations on a 32-way server, the processing time took about three months. After moving those simulations to a grid, processing time was cut to about two weeks.

Dan Kaberon, director of computer resource management at benefits outsourcer Hewitt Associates said he's able to use IBM's Smalltalk object-oriented programming language on a grid without a per-node charge, unlike with some other options he looked at. Hewitt moved its pension calculations off an IBM mainframe to a grid, making the grid, in effect, a "co-processor" to the mainframe.

Grid computing's licensing may be in a state of flux - if not confusion. But the way forward for end users today would appear to focus on open source, which avoids many, if not most, of the problems associated with commercial software. And if enough users follow this path, the business lost to GPL-based vendors will concentrate the minds of the commercial vendors.