Three open source start-up executives Tuesday showed their daring by making  pitches to potential customers. What made them daring is that they did it in front of dozens of attendees at the Open Source Business Conference in Newton, Mass.

The presenting companies were ActiveGrid, EnterpriseDB and XenSource. Customer panelists hailed from the Commonwealth of Massachusetts, Fannie Mae and financial firms Fidelity Investments, Putnam Investments and State Street.

Not surprisingly, the customer panelists who agreed to participate are from organizations that use open source software, though some to much larger extents than others. Their responses to the new companies ranged from practically inviting them in to show off their software to telling them to get back in a couple of years.

First up was Peter Yared, CEO of ActiveGrid, which is offering application servers designed to talk to multiple data sources (including Web services) and that boast rich user interfaces.

Fidelity's Charles Brenner, senior vice president with the company's applied technology center, immediately poked fun at ActiveGrid, noting that he used to tell people never to buy anything from companies with the word "open" in their names because the products always turn out to be closed. "Now I tell people don't buy anything with the word 'grid' in it," he said.

But Brenner said one concern he has with any open source technology is, "What happens if it dies?" In the case of ActiveGrid, he wondered what the output of its application builder would be and whether it would be something his team could recode by hand if need be. Yared assured him that the software would deliver largely standards-based applications.

Fannie Mae's Rick Carey, a vice president in the office of the CIO,  called ActiveGrid's idea interesting but said, "I worry…  that your space is being commoditized already."

Tim Vaverchak, director of Massachusetts' IT Division, was curious about how the company would work with the open source community and integrate that into its business model.

Next up among the vendors was Andy Astor, president and CEO of EnterpriseDB, which sells database software that it positions somewhere in between the PostgreSQL open source database it is based on and traditional proprietary databases, such as those from Oracle.  Astor claims EnterpriseDB's offering is more robust than bare bones PostgreSQL and far less expensive than Oracle's software.