There's much more data in the Programming Languages field, which contradicts this study:
Let's look at the popular dynamic languages, where progress is either hindered by the original author still working on it or stepped back, or where progress succeeded, when the original author is there or not there.<p>* ruby: matz still there, stagnating progress (sound but slow design, desperate implementation problems)<p>* python: guido still there, steady but slow progress (sound but slow design, proper management at least)<p>* php: rasmus still there, but thanksfully not really. with less rasmus, more progress. esp. after hhvm and php7. (unsound design, unsound community, but external pressure improved it radically)<p>* perl5: larry went away, decline (unsound design, unsound community)<p>* parrot: authors went away, death. (even with sound design, which was later destroyed by community)<p>* perl6: founders still there, progress. (sound design, huge implementation problems)<p>There are many more examples, but this is the easiest summary. esp. with the lisps, which all have a sound design and a single author.<p>So we have both, positive and negative influences:<p>* when the original design was sound, but the author went away, it will decline.<p>* when the original design was a hack, and the author went way, it might progress.<p>* when the original design was sound, and the author is still there, perfect.<p>* when the original design was a hack, and the author is still there, decline or death.