Success is relative and is defined by the size of the market and one's market share. So when do I give you your next class in economics?
That's just one way to define success. Success, the word, without context, could refer to completion of a difficult task, or a sense of accomplishment, or any of a number of other things.
NetBSD has never sold a copy. Does that mean it's not successful? You might say yes, but considering how well we're fulfilling our primary objective (to make available a highly portable OS), I think it's damned successful. I feel a sense of accomplishment whenever people use code I've helped improve. So maybe the guys working on MorphOS feel successful - it's not up to you to decide whether they do. It's up to you to have your own
opinion, though.
Another example - if someone who's making $50k a year and is living very comfortably and not spending more than he/she makes feels successful, yet another person who's making $100k a year is spending more than he/she makes, is the first person more or less successful than the second?
The point is you can't just go around making blanket statements while assuming that everyone is just going to use your definitions for everything.
