Is there an accounting or ERP package, either closed- or open-source, that has clients that run on Windows, Linux, and Mac?
- It does not matter if it is a free or paid solution.
- It must also be a "thick client" solution, not something that runs in a web browser (there is a specific business reason for this so it's not negotiable). If you provide a product/solution that runs in a browser, I will at least give you a point in recognition but I won't be able to accept it as an answer.
- Solutions that provide source code are given special consideration and will be more likely to receive the accepted answer, as this is for a highly-dynamic business environment, where requirements are changing weekly, or even daily.
Clarification: the idea is that, whatever the package is, you would be able to migrate between platforms (or use all three, if needed) and not worry about migrating your accounting/ERP. The point about web browsers is a deal-breaker, please don't bug me about how it would be "easier" as this is someone else's requirements, so it's not something I can control. Source code is a very important factor as a canned package would not be expected to live long in this environment.