POS software free for ubuntu

I have tried this http://ift.tt/1wYHQvB and i is free and does every thing i whant but you have to pay for some fetures after 100 sales but i do not whant to pay for it. if any one could sugest a alternative

thanks

POS (point of sale system)

Ubuntu 14.04 lts 4gb ram 3.6ghz 32bit Dual Boot windows 7