The Foo licensing plugin looks good. We created our own licensing technology (also with lots of one click no hassle upgrades) for FV Player but Foo Licensing this had been available a couple of years ago we would have been happy to save ourselves the trouble. We'll definitely take a look to see if there's any chance of sharing code here and consolidating on a single product.

The third party marketplace for extensions sounds like a great idea. If the extensions are inexpensive, it's almost always better to buy than roll your own.