Need unlimited installations (or domains) license

I nearly got sick right now after a huge disappointment. I was installing PowerStore which I bought 6 days ago and was very enthusiastic about getting it to work. I figured it probably worked similar to Webassist’s eCart and since I already used eCart this would be easy for me to figure out. Then I can start using it to offer shopping cart’s to potential clients. It was all great until I found out I bought a Single license....Gosh!. I can run the eCart extension on many websites so I thought the PowerStore worked similarly. I was trying it out to offer it to a potential client but at the price for a single license, my profit margin would be small since I don’t charge much for setting it up. And then if I set it up for any other client and then they backed out, I would be stuck with the extra expense. Goodness Gracious, there are Open Source solutions out there.....Why would you sell us a Single License? I am an individual working from home...can’t you sell people like me the product with an unlimited installations license? I think I’ll end up cancelling it after the trial period.