The kanji reads daikichi (great luck). I made a version using seal script too. I stole the idea from one of my teachers in shodo who would use a daikichi stamp to balance his name stamp. I made both of them in photoshop. Basically I used the shape tool to make the hanko shape, then I used the text tool to write the words, then I colored in the box or just the text. Then I made the drawing into a brush and I just one click that brush, making it more of a stamp. I'm not sure how you could do that with your freeware program, but that's how I made it in photoshop.