My company is going to rollout a Application server architecture based software (Ref Software Architecture.jpg) which uses the following tools for development (Ref:Tools & Technologies.JPG).

There wont be any confidential / sensitive data that is going to be stored. Also there wont be much transactions taking place and no backend procedures would be used to ease migration.

The desktop version works on the following platforms:
Windows
MAC
Linux
Solaris

The PDA version works on Windows Mobile, Palm, Symbian & Blackberry

The software requires syncronization between any of the desktop version and any PDA platforms.

Inorder to reduce cost I prefer to go for a low cost solution like MySql (a fees has to be paid since the s/w is for commercial purpose) or PostgreSQL or IBM Cloud Scape.

Which one would you suggest?

please do not post into multiple forums, thanks