Open-source enterprise software developer OpenLogic wants open-source users to stand up and be counted in a worldwide census -- and is offering a new software tool to help the process.

The number of licenses sold gives vendors of proprietary software a pretty good idea of how many people are using their code, assuming there are not too many pirated copies in use, or licensed copies gathering dust on shelves. They can also draw on information about paid upgrades or service contracts, or sell unique license keys, verified by a central server each time the software is installed -- or even used.

Open-source software developers have no such luck: the very nature of open-source licenses makes such verification methods impossible. One clue they have is a count of how many people have downloaded the software from their Web sites. Reaching 1 million downloads is a rite of passage for open-source projects: SugarCRM, for example, passed that landmark in May.

Such counts, though, may underestimate the number of users, as anyone who obtains open-source software is free to redistribute it by any other means they choose -- as long as they accompany it with a copy of the open-source license and make the source code readily available.

On the other hand, they may wildly overestimate the number: people may download the software with no intention of using it, since there is no financial disincentive to doing so, or they may download it multiple times if they upgrade it, wipe and reinstall their system or have several computers.

To come up with an accurate figure for the number of users of various open-source applications in the enterprise, OpenLogic has released an automated census tool, OSS Discovery, itself available under an open-source license.

It hopes that businesses will scan their machines using the tool and contribute the data about the applications they are using to an open database.

The tool could offer advantages to IT managers too, said OpenLogic, enabling them to build up a picture of the software installed on desktops and servers around their business and compare it with that used in other enterprises.

OpenLogic is looking for partners to distribute or deploy the software and wants open-source software developers to contribute digital "fingerprints" of their applications that will enable the discovery tool to identify them. Those who help with the project will be offered access to the anonymous data gathered.

OSS Discovery 2.0 is based on the company's OpenLogic Discovery tool and is distributed under the GNU Affero General Public License version 3. This recently introduced license extends the GPL license to ensure that changes to software used to power publicly available services will be contributed to the free software community, even if the modified software is not itself distributed.

OpenLogic hopes to begin collecting census data early next year.