A US startup has developed software that enables Linux users to donate their machines' idle processing power to help run tasks for commercial and non-profit projects.

Users can download Popular Power's client software on their PCs which kicks into play whenever their machines are idle or have spare processing power. If the PCs are online but not being used, the software automatically alerts Popular Power's website which distributes small tasks for the systems to process.

Current projects include a non-profit research application that uses computer modelling to help better understand flu vaccines. But according to Popular Power chief executive, Marc Hedlund, users will in future be able to donate their machine's processing time for commercial tasks, such as movie rendering, for which users will receive online gift certificates or frequent flyer miles.

Popular Power's software was originally released for Microsoft Windows clients last April and a version for Apple Mac clients will be available during the summer.

According to Hedlund, several hundreds of thousands of the Windows version has been downloaded since its launch and several hundreds of Linux versions are already in use.

Tasks can be carried out when users are at lunch and the workload can last between 15 to 60 minutes. Like a screensaver, users can stop the work and take back full command of their machines by hitting any key.

Hedlund promised that the tasks would not interfere with or pose a security risk to users' machines because the workload is carried out within the confines of the Java Security Soundbox. This ensures that the program does not interfere with the machine's disks or modems, he explained.

The software requires Pentium-class machines with about 32Mbs of RAM. The size of the workload varies between 50Kbs - the size of a graph on a website - and 1Mb.

The company also plans to make available an open source release of the software early next year.

Nelson Minar, the company's chief technology officer, said: "Linux users fuelled a number of early distributed computing efforts, helping the field advance to where it is today. Strong feedback from our web site made Linux the most requested new system for us to support."