Making a game is one thing, selling it is completely another deal. The last things you should worry about is stealing code or models from you game. Actually if anyone tries to steal something and you learn about it, you should be flattered 
. But I bet no one will ever steal anything and try to make profit of it. Justā¦game business is a lot different than simply making games. 
And I think this thread is one of thoseā¦leading nowhere.
Many of the previous posts have valid points. In the end it depends on what the project demands and what the team is comfortable working with. There are many other free open source alternatives such as Godot, JMonkey, Torque 3D, but none of them gives a complete package where you can do everything except for audio editing. The game engine can be extended to do some amazing things, even laboratories uses the GE for physics simulations with python code. It can be opened to use modern OpenGL.
The GPL may seem like an issue for some, but many do not seem to understand why Richard Stallman created GNU and the GPLās in the first place. I feel safer knowing that code is open to the public to see, instead of proprietary, where there has been cases of games sold which used players systems for Data mining and even for Bitcoin mining.
Blender is a great tool which works out of the box on most systems without installation, it is great for educational purposes as well and costs nothing. Maybe it is time that the Blender Community band together to create a AAA title just to prove the skeptics wrong.
I donāt feel like reading three pages, but some things need to be said.
Unity 5 has tons (pretty much all) of the old pro features for free.
The only thing I can think of that BGE has that Unity doesnāt is having the object that path finds also be an obstacle.
^^ Good Job BGE 
Unity doesnāt have a complicated license. If you make $100,000, you have to buy pro. Also, Unity is super easy to make Mobile games for. 
This is the main reason I think that there are SO MUCH shit out there on the internet. Stories in games for example, have anyone ever thought of walking up to an author who has published a great book and asked them to help out with their gameās story. I donāt think so, there are places on the internet where people have creative writing stuff going on. Theyāre masters of storytelling but nobody ever asks for advice or help from them.
Extra credits covered this if you want to look up their video. Summary: DONāT START WITH A STORY. Writing for games is not the same as writing for video or literature.