GPL copy half a page from a primium theme

I have a GPL question since I know very little of it. I'm designing a site for a client and we found a theme that is free, but the client found another theme (not free) to use for the homepage. So I'm planning on using a drag and drop builder to create about 1/2 of the design of the home page from the premium theme. Do I have to purchase the theme to copy the design of half of one of it's pages?