Going to the source: dBASE accounting. (includes related articles on choosing a development tool, and response to a splintering dBASE market)

Off-the-shelf accounting packages don't always fit a company's accounting style. The companies that purchase canned systems often discover that they have to change their accounting practices to match the software. These changes can range from redesigning invoices to restructuring the chart of accounts. On the other hand, canned accounting packages are usually well tested and available for a wide range of business needs and budgets. For the ultimate in flexibility, look to custom software. A program written specifically for your business' accounting needs can minimize the compromises and sacrifices you'd make for the sake of computerizing. But custom accounting packages aren't usually for the budget conscious. Along with the investment in designing and creating the program, there's an investment in employee testing time and bug reports, training, and more. The transition period for custom accounting packages is significantly longer than the time it takes to convert to a canned accounting package. Before deciding to go with a custom program, you'll have to do an in-depth system analysis, create the design, and see if you can justify the cost.

Source-code accounting packages cover the middle ground. They fill a practical need for a system that's been rigorously tested, yet provide the flexibility of custom programs. Basically, they're designed for general accounting use. You buy individual modules as you need them (for example, general ledger, accounts payable, and payroll). The vendor provides the source code and, often, detailed technical documentation. In theory, you can then modify the system's source code to fit the needs of your business. Like canned packages, these products come in a variety of shapes and forms-each with different interfaces, restrictions, and prices. If you're a consultant or developer who needs to select an accounting system for a client or upon which to base a vertical market application, you have much to consider. As with all accounting packages, your choice should follow sound accounting practices and have the necessary modules available. You should look for a system that's closest to your current …