For me "Open Source" is not about "free software", But mores about it :
1. Community - For support and enhancements.
2. Access - Fast and easy to try out.
3. Cost - Individuals get a opportunity to use good quality software.
4. Support - Due to low cost a large number of individuals have knowledge and is supportive.
5. Transparancy - The source code is open.
I would say:
- community support
- faster bugfixing/development
- portable to different platforms
- reviewing sourcecode if the company requires thorough evaluation what the software does before implementing.