It's here.

And it's not freeware. Just because it's old doesn't mean it's free.

Definitely isn't in my public domain 80s games collection.

http://www.mobygames.com/game/popcorn/techinfo
Here is some proof that it's freeware/public domain and not all of the old games on mobygames.com are freeware and i now that but according to this the games freeware and here is more proof
http://www.mobygames.com/game/dos/popcorn/trivia
Look at both pages and that is enough evidence that it's freeware. I am sorry if i am wrong.

Some sources:
http://www.theswapmeet.com/articles/raynal2.html

Popcorn was released as freeware. The game went around the world. We received tens of thousands of letters from everywhere telling us it was the best game. Compared to the PC version of Arkanoid, which was really dreadful, Popcorn was 10 times better. We acquired quite a reputation in the process.

http://forum.magicball.net/showthread.php?t=5736

POPCORN is a FREEWARE which is gracefully offered by LACRAL software.