"Photoshop" has become a generic term for any similar graphic editor, in a similar way that we talk about googling. When someone says an image has been "photoshopped" it does not necessarily mean that Photoshop was used, only that it has been edited. GIMP has nothing to do with Photoshop other than it's a graphic editor and happens to be free.
I came across a site that had many well-known programs at a fraction of the price but online download only, no support. I didn't note the URL. It seemed legit but I was very dubious. At best, you would have no recourse if the software did not work.