Selling abandonware

You answered your own question. You don't have rights to it. Current copyright law gives the owners until decades after they die.

There is NO SUCH THING as abandonware!

HECK, I once found a program that is effectively public domain! I was given SOURCE CODE to it, and allowed to rewrite and even SELL derivative works! People ALL over are ALLOWED to copy it. At the time, that portion of their site wasn't monetized. HECK, some are practically FORCED to download it, at least the runtime! Well, I wanted to create a kit of sorts, and figured it would be a good addition, as a premium, NOT something to be charged for.

I didn't want to get in trouble, so I asked their lawyers if it was OK. Even THEY were given pause, but THEY SAID NO!!!!!!!!

BTW The product? Sun JAVA!

And WHO KNOWS if they are selling it anymore, etc.... Sometimes things have names changed, are incorporated into other products, deemed illegal, etc... A good example is the early lack of 128bit software from the US. Some companies didn't sell it abroad because it was a FELONY to do so. Luckily, those laws have now been rescinded.

Steve

CGP is selling an installer that installs a copy of DOSbox (a free program) and configures it with settings that work best with the game in question.

They can do this. It's legal.

They also include a copy of the game free with the download, using various hand-wavy justifications of why they should do that.

Can they do this? Maybe. It's not entirely clear. But if the copyright holder asks them to stop, they will - and that's all that can be done.

Easier to ask forgiveness than permission, and all that.