Yes, there's no way that somebody could have a product called OpenOffice that is literally an Open Source version of Office. Impossible.

The legal purpose of trademarks is to serve the same purpose as a signature: in order that one company cannot do business pretending to be another company without showing a clear intention to defraud - an intention made clear by the attempt to fake a signature, or imitate a mark. It is not to own words or sounds. It is a mark that you trade under.

This is a product that is openly hostile to the other product, and is adding a well-established prefix to indicate the reason for that hostility.