Even though this fan-made series uses HTF as one of the source materials, there are some distinct differences between the web show and the fangame series.

Happy Tree Friends Happy Tree Friends Adventures
Characters can die almost every time. Characters rarely die (in-game, deaths can occur mostly due to player mistakes).
Unclear main villain (not counting the Ka-Pow! shorts). Has a clear main villain.
Obviously, only features the original characters from the show itself (with few exceptions). Features more than just the canon characters.
Exaggerated injuries and deaths. Injuries and deaths are a bit more realistic.
The characters speak gibberish (with the only exception being the narrators (and the interviewer from "Intimate Spotlight") in certain episodes). All characters speak clear English.