The English language, for all its glory, has never created a word for this, despite having two words that each might be its opposite: envy--the dissatisfaction that comes from resenting other people's well-being; and schadenfreude--the pleasure that comes from delighting in other people's misfortune (borrowed from german, it's fairly common english parlance). That my culture has never required this word to reasonably describe our world might be the single most embarrassing thing about it.
We have a not too terribly obscure word that describes a bit of plastic on the end of a shoelace to keep it from fraying, but no word for joyous appreciation of the success of others. Perhaps this partly explains why modern capitalistic society, the roots of which trace through dozens of American Secretaries of the Treasury and then to British economic theory (so, um, banking) has decayed into an egalitarian farce, with a wealth divide as absurd as it was in the darkest days of the DARK ages.
For more information check out the wikipedia article on Capitalism. Especially this amusingly brief section titled Systemic weaknesses. Reading through this article, you'll find reference after reference after reference to how Karl Marx famously wrote about what a clusterfuck capitalism is. It's honestly depressing. For a minor pep-up, read Post-capitalism, and for a slightly bigger one, read Post-scarcity economy
Stories I hear about people like these three magnificent fuckers make me earnestly hope that the syndrome of selfishness, envy, and jealousy that plagues my culture, and to a large degree the entire world, and that kept the word and therefore the concept of mudita from spreading, has run its course or nearly has. If that thought gives you hope about our species, help me spread the word. Mudita: your success brings me joy.
Aloha kuleana, my darlings. Love is our responsibility.