I'm getting more and more annoyed at people on the internet. Yeah, I know, how can that possibly be? Unusual stuff!
Shortly put; it's the label "Indie". I love that label, and for me, that has always had a rather simple definition. Indie means independent. In music and movie business, it means that the creators are independent from any record labels or publishers that usually own part or the whole of the artist or production team. They stand on their own legs and handle most things themselves that a publisher usually would, and must deal with the expenses themselves, and all that.
For me, it has always been obvious and natural to assume that indie, when it comes to game development, means the exact same thing.
The game industry is in some ways very similar to that of music and movies. The usual scenario is that we have a publisher that sits on a lot of money, and give you (the creator) some of that money in order to produce something that the publisher can publish. They invest money in you so that you can create something that will earn them the invested money and a profit.
If you don't have a publisher or similar more external investor or owner, no middle-men that control your creative process so to speak, and fund everything yourself using money coming directly from your own (personal or company's) pocket or directly from sales, and make all your own decisions being your own top dog, then you are indie. You are independent.
Yet for some reason, people online tend to argue that selling a lot of copies of a game makes you less indie. Or, forming a company makes you not indie. The company is still independent.
Example: Dice (the creators of Battlefield and Mirror's Edge among other games) are not independent as they depend on Electronic Arts (their owners). Mojang (the creators of Minecraft) started out as one guy making a game and ended up in a small company which is still independent as they are their own owners.
I hate when good and descriptive labels gets watered down.