I realize you have spent time (which is money) in developing your accounting package but you should be looking at getting a product to run on linux. Today, selling a generic accounting package will not put food on the table. Currently, the only way to make money is to offer services. If you can show the client that he/she will save money by moving to Linux with all the benefits that are currently available on M$ windows they'll buy your solution.

The other problem is all the small and big accounting packages are so similar that it is impossible to figure out the differences. QuickBooks can do all the generic things the AccPacc's, AccountMate's and Mas90's do. But when you start to realize that there are only minor differences between all of the mid-level systems it gets scary.

Just think of it -
GreatPlain small business -- $995.00
QuickBooks Pro -- $400.00 has programmers API interface
BusinessVision -- $3000.00 32 accounting modules
AccPac simple Accounting -- Free
SQL-ledger for Linux/windows - free
FreeMoney for linux/windows -- free

I'm sure there are many more I missed.

If you have a vertical like in the printing business, food dist, or warehouse dist (you get the idea) you might make money. Or offer your services in the linux market and get the money they would have spent with M$ products.
John