Read the thread that Dutch quotes above. According to that thread, and one of the blokes there is an original Red Baron guru, it looks like the real deal, but a lot of the information in the spiel on the advertising page is inaccurate. (The BOX in the picture of the game IS the box from the original Red Baron 3D game, but the written information appears odd.
NOTE: the thread Dutch quotes refers to the following URL: http://www.gog.com/en/gamecard/red_baron_pack,
is where I would be spending my money. I would be more reluctant to buy from the site YOU mention because of the way the advertising on that site is written. (For example, the REAL Red BAron game supports 64 or 128 players (or something of that order) on Massive Multiplayer.) It might not be the real deal or it could be a rip off. Also it could be the ARCADE version of Red Baron which came out a couple of years ago. Also, the Gog site is mentioned by people on this forum who REALLY know their stuff - ArgonV, and other.
Once you have Red Baron3D (or RBII) all patched up as described at the beginning of this thread, it is most definitely NOT an arcade sim.
I still fly it and love it after 10 years.