Unity is charging per install (not per sold unit), so technically developers can owe Unity more money than they make.

Not necessarily. Unity says they're charging per initial install once you break $1M (they walked-back on the "every" install bit), but Unreal takes a cut of your royalties once you break $1M, so it's still hard to really compare them properly. If you're making a free to play game, your install number could be dramatically higher than what a non free-to-play game would need to break $1M, for example.

They're pretty different.

Unity is planning to charge a flat fee of $0.20 per install over the entire life of a game. A Triple-A developer can release a game for $70 and it earns ten million dollars. Assuming every customer installs the game maybe three separate times on average over their lifespan, Unity's gonna take maybe about $85,000 in total in runtime fees. If the game had been developed in Unreal, Epic would have taken $450,000.

But let's say an indie dev makes a great game in Unity, sells it for $5, and it goes viral (like Vampire Survivors). They make ten million dollars, Unity takes 20 cents per install, and assuming the same install rate, the bill comes to $1.2 million, over 14x what the AAA developer is paying. Epic would have still charged $450,000.

With the AAA example, Epic's 5% may seem steep for games that cost a lot per unit, but at least when a game stops making money, they stop charging money.

For Unity's runtime fee, though, as people buy new PCs/consoles/phones and install their library of games to them over and over, the developer keeps getting billed with no profit coming in. Effectively, the more games they have out there in the wild, the greater a financial burden a developer has. They'll be living in fear of some Reddit post sending 10,000 people in /r/gaming down a sudden nostalgia trip and wake up to a $2000 bill the next day with seemingly no explanation.

And this is to say nothing of the problematic nature of how Unity would even accurately assess the install count of a game, or differentiate paid copies from promotional or pirated copies (which I doubt they will). Or if a developer wants to bankrupt a rival developer, how they could just rent a click farm in Malaysia to install a game over and over again and rack up a bill too high to afford.

It's a full engine! It specializes in 2D games but their 3D support is growing rapidly, just not up to what Unity and Unreal offer right now. Here's a showreal they did for games released using Godot last year: https://youtu.be/UAS_pUTFA7o?si=QuPq6hByt-lve-vg

Godot is a full engine, I would position it in the market somewhere between Unity and GameMaker Studio. It is capable of making 2D and 3D games, though there's some things Godot lacks, for example the asset streaming capabilities that allow for large seamless open worlds without loading screens, they're working on that.

Godot runs on WIndows, Mac, Linux various BSDs, and they're working on an Android port. Godot games can be exported to Windows, MacOS, Linux (and thus SteamDeck), BSD, Android, iOS and the web. Godot games can be ported to consoles, but Microsoft, Sony and Nintendo are really fucky about licensing. The way you would go about publishing your Godot game to Playstation, Xbox or Switch is to work with a porting company who specializes in such things.

Fun fact: The Godot IDE is itself a Godot "game." The Godot editor runs in the Godot engine and is built from UI tools available to end users; this makes it pretty easy to create tools and extensions to customize the editor to your team or project's needs. It's also a practical demonstration of how robust Godot's UI creation tools are; I've been toying with the idea of building a woodworking CAD program in Godot.

I have literally no idea. It just pops up left right and center so it seemed it is a competitor.