I checked the Turnitin web site term of use.
Shlomo Geva

In regards to the TOS mentioned in my original post, they are linked in the post, and are at https://turnitin.com/agreement.asp

Although a version of the exclusion quoted does appear in both TOS/agreements, the immediately following clause says “You grant Turnitin a non-exclusive, royalty-free, perpetual, world-wide, irrevocable license to reproduce, transmit, display, disclose, and otherwise use your Communications on the Site or elsewhere for our business purposes. We are free to use any ideas, concepts, techniques, know-how in your Communications for any purpose, including, but not limited to, the development and use of products and services based on the Communications.”

In my mind, this revokes and contradicts the previous clause: “We are free to use any ideas… for any purpose” is not at all limiting their usage.