It is safe.
The script on the page can be saved in your home folder, marked as executable, then run.
Or...
wget http://pol2095.free.fr/flash_player_sa_linux.x86_64 -O flash_player_sa_linux.x86_64.tar.gz
Extract the file and use it as a Standalone, without installing.
Which is what I do.
Double click the Flashplayer to launch it. Then click File > Open and navigate to the file you wish to open.