Wow, this is big news! Adobe has just announced that they will be releasing Flex under the Mozilla Public License. If you think about it, it's not that big of a jump since the Flex SDK is already available for free, they are just releasing additional developer resources, docs and build information...and enabling outside developers to contribute.
The press release: http://www.adobe.com/aboutadobe/pressroom/pressreleases/200704/042607Flex.html
This seems like a smart move to me for many reasons. First off, it's hugely positive PR. The public loves open source. Adobe has gotten a bad rap for the cost of some of their enterprise products, despite the fact that they have contributed to many open source products and released their own (Tamarin). This is a big step towards broad acceptance of Flex by the web development community, and it's going to have a great impact on the success of Apollo. If Adobe wants to rule the web, this is how they are going to do it.