How many of those run on the web as a platform? (A cursory search suggests 'not many' or 'not without some effort'?) There are some components I'd ideally like

How many of those run on the web as a platform? (A cursory search suggests 'not many' or 'not without some effort'?) There are some components I'd ideally like to avoid rewriting for my web and desktop applications. (E.g. why should I have to write render code for my friends list component more than once?)