Thanks. I did a little googling. It appears that Silverlight works (at least marginally) in several browsers on two OS's (Windows and OS X).
I'm still curious about why Silverlight works for, say, Firefox on OS X, but not Firefox on Linux. I understand that Microsoft probably wants to prevent Silverlight from working on Linux, but I'm curious whether it's something hard to do because Linux doesn't have X, Y, and Z that Silverlight requires, or is it relatively easy to do (if you had control of the codebase).
I don't use it, but the trypython.org page has a statement:
"Target browsers are Firefox 2 & 3, Safari and IE 7 & 8. (It won't work in other browsers until there is a version of Silverlight that works with them.)"