As long as it's freeware, it doesn't matter thát much, but to be on the save side, don't use Pong as a name solo.
There have been some games with names like UltraPong, SuperPong, Überpong and what more (those all exist for real and are (cool) Pong clones by the way).
With a little bit of creativity you can think of a better name than just Pong.
