The flex sdk was free and open source since 2008. “Flex Builder” aka “Flash Builder” was an IDE by adobe that cost money, but you could compile and build flex projects without their IDE.
There are some open source flash players for linux, but I don’t know how good they are.
In general I think that there a lot of good ideas in the worfklow and constructs of some of these older frameworks that maybe get looked over since the projects never gained traction or failed somehow. Or perhaps 90% of an old framework or language is terrible, but 10% of it was really good, so let’s focus on that good part.
For example, VRML is really interesting, really old school virtual reality in the browser. Objective J seemed ahead of its time, at least the UI components it could render were pretty mind blowing at the time.
I just wonder if there are any great gems in these old projects which were irrelevant at the time but make perfect sense now. Maybe I’m just too nostalgic of a person and need to let go So much new stuff is coming out everyday that it’s hard to keep up with, and also try out some older frameworks and ways of programming.