That person is actually wrong about that. Games in splore are put there manually by their creators. You can export your pico 8 game in a binary format that both does not require pico-8 to play and doesn't show the source code.
As far as I know SPLORE only shows you games that have been uploaded to the BBS. So it would be possible to create a game, make a execuatable, sell it, and never have it available on SPLORE. @Poxy
