The Open Source Census is a collaborative project that collects Open Source usage information from companies that volunteer the information. The OSS Discovery tool requires Ruby to be installed on a system to be run. The tool collects fingerprints of many Open Source applications on the scanned computer (it does NOT crawl the network). The results are submitted anonymously to the project.
The project was started by OpenLogic and is sponsored by numerous entities including Collabnet, IDC, Microsoft, the Open Source Business Association, and the Oregon State University Open Source Lab.