I'm not sure I'm fully understanding the various licenses associated with these "royalty free" photos, so I thought I'd simply show what I had done with one to make sure I've done things on the up and up.
Here's a photo that I used, having purchased the smallest one:
I named those two individuals "Michael & Michelle" and took the photograph into CorelDraw, creating a "logo" for "Michael & Michelle" to use in a question and answer document concerning a new service for a home inspector trade association. The document in question with "Michael & Michelle" can be seen here:
It's a one-time document that can be viewed by about 9,000 people at http://www.nachi.org.