Well, the problem here is also the target market. If we're working on this as a small desktop app, then a significant portion of the users aren't going to have a database installed, regardless of whether they're a Windows user or *nix user.
The best option might be two separate versions; one that's DB driven, and select a "required" DB like MySQL, and one that's CSV driven. The CSV version would satisfy the cross-platform requirement (done properly) while the MySQL version offers higher performance.
As for project management and communication - we're working on that one.
- Ozymandias