infoQ seems to be down but here’s my 2 pennies worth:

… the only thing that persuades them [a developer] to use a technology is a critical mass of peers also using it – in other words reluctance to invest learning time in something that becomes defunct. The technology will only get better through use, so any arguments regarding familiarity of Run Time / Compilation / Dev Environment are irrelevant.

Following this idea through to its logical conclusion, Open Source or Proprietary, the only thing that really matters is whether or not the technology is achieving what the market demands.

The plugin does have a long history of being improved and available, … on Windows (and somwhat Mac too). For a long time, linux people were second rank citizens with respect to flash content. The player sucked. It is only recently, that the player has had good, official releases for linux.

If it was open sourced though, linux dudes could build 64 bit versions, or .deb packages, so it was as easy to install as everything else on a (debian based) linux distro, …

Or, if it wasn’t open sourced, they could just open up the development process a bit. For instance, by letting us follow in the bug tracking.

I *am* using flex myself, … for an app to some customers running windows. I am not sure, that I would bet a real commercial application which was targeted for the linux platform, on the flashplayer.