Easy, by stripping all adult content and putting it in a patch like every other game. As long as it is easily distinguishable from the main game its art comes from, it would be because these characters are not default characters, and no adult content is in the actual game files, this one is where the real problem is for heavily adult oriented games, they'll allow it.Okay but then how would it be able to get on Steam using Honey Select? Barring all adult content, Harem Hotel still wouldn't be able to release on Steam because then they'd be making money off of it
In case you meant because Honey Select is an adult game itself, that is true, but content from the studio is only as adult as the creator of the project the studio is used for makes it. You can very easily make completely nonsexual content in the studio. Runey could literally make a picture of Lin standing there doing nothing and it isn't automatically adult content just because it was made using assets from an adult game.
In case you meant the making money part, since Steam is a platform for making money in the case of the developer side, another easy one. The developer would be making money off their game, not the assets.