[grey-area]

You haven't defined it at all, and I think if you try, you'll find it hard to differentiate between the use of capital to start a business and the use of capital for one of the other activities I listed above which bring in income with no effort. All are using existing capital to earn more.

Forever, if they don't keep putting something into it? I don't know about that.

If you accept that banks should pay interest on deposits (forever), or shares should pay dividends (forever), then you accept that owners should receive money forever for an initial investment, just as other holders of capital do for other investments. There's nothing nefarious or unjust about it.