this is easyPOS.
easyPOS is a GTK+ based cash register program. now that you have imported the source tree, you need to create a bin directory on your home directory unless you already have one. all easyPOS executibles go to your home/bin. now, you can "make" the system. before you can run the register (reg2), you should look at the directory "/goods". this contains a copy of our menu as a series of flat files. you can either modify and run format_slip or at the least create /slips/200x/Mon(th)/dd. eg: /slips/2000/Dec/25 for the current date. The /credit directory contains a sample creditor (j random hacker) and two required entries. your machine should have a printer and the standard lpr queue.
some hardware notes: i bought a slip printer with a parallel interface and simply set up a printer in linux. slip printers have an output that triggers the cash drawer when you send it an ascii bel. this has been running fine for a year. the host machine is a p-200. it has 64 meg. i recommend a 17" monitor, tho we have used a 15" now for a year. for backup, i have been ftping the day's slip directory over to another machine at the end of the day. near the beginning of reg2.c, there is a #DEFINE DEBUG statement. removing this enables fancy print options for the register tape that make havoc with a regular laser printer (extra form feeds, etc).
needless to say, your machine must be configured for GTK development. i have been using RedHat 7 via the krud distribution.