i figured there were some specifics on the osCommerce side to be conserned about,
if not then maybe for example Zen Cart bitcoin module can be used without much modifications?
there is no need to reimplement the actual bitcoin client at all,
the payment module just needs to
1. give customer an order specific address to send payments to(new address is created for every new payment for security reasons),
2. record customer return address(in case order is canceled and funds must be returned)
3. and monitor from running bitcoin client when the payment has been received