The quality of the initial open source package is certainly a huge decision factor. In healthcare, not many comprehensive open source packages are available. The Veteran's Administration (VA), however, did release with OpenVistA a very comprehensive EMR product, used in the daily operation of over 130 VA hospitals and clinics across the nation. OpenVistA was registered with SourceForge in 2003 and receives about 100 downloads a day, which is considerable for a specialized EMR system. OpenVistA has been translated into several languages and implemented in many hospitals outside the U.S., which shows the potential of open source for global cooperation. Currently, it is based on MUMPs and C#, but since it is open source, a potential user could re-write the front end, for example, in Java, to make it platform independent. Another emerging open source package comes from Tolven, which is more focused on the needs of primary care physicians and personal health records.

Example by @StephenFleming of a successful FOSS software project by the VA, they created an EMR system and open sourced it.

Open Source in Healthcare: Cui bono? - Healthcare Information Technology