Adobe’s Flash products are 100% proprietary. They are only available from Adobe, and Adobe has sole authority as to their future enhancement, pricing, etc. While Adobe’s Flash products are widely available, this does not mean they are open, since they are controlled entirely by Adobe and available only from Adobe. By almost any definition, Flash is a closed system.
Steve Jobs has recently come out into the open about his feelings for flash and the adobe suite as a whole. This may lead to Apple either banning adobe from Mac OSX, or it could mean that adobe may need to make a Mac OSX specific version of the suite.
If Steve Jobs does ban the adobe suite from Mac OSX this could lead to a dramatic fall in OSX and Mac sales for Apple. As people who want to use the adobe suite will have to use Windows. Mac has been the design platform, it has been used for design, graphic and multi media work. Getting rid of adobe on Mac would mean there is no reason to purchase a mac any more.
Flash will still be going for years before the implementation of HTML 5. This is due to websites being re-coded and remade to incorporate HTML 5, so you mac users will have to wait a while longer.
If your looking for a good read Steve Jobs’ open letter can be found from the link below. It goes into more detail than I do here.