Come again?

Here is a Flash developer, talking about why he thinks "open-sourcing Flash isn't the way to go". The core of the argument is the following:

I like knowing that everyone's version of Flash player is exactly the same. I don't want to have to start hacking applications to make them work in the 2-3 most popular versions of the Flash Player. For me, that's the single biggest reason why open sourcing the Flash Player would be a bad thing.

In response to reason numero uno, why? Why is this so important? I'm genuinely curious. Why is version proliferation such a bad thing, especially when it is known that the most used versions will ultimately become the most common, forcing out those that simpy don't cut it for their user base? And in response to reason numero dos, again, why? Why is this so important to you? Why would you have to hack these applications to get them to work in the "2-3 most popular version of the Flash Player"? Why would there even be "2-3 most popular versions" rather than one which will float to the top? There are tons of free software applications and most of them don't suffer from the kind of version proliferation so dreaded by this gentleman. Development tree mergers happen all the time to take care of that - if the user community and the developer community demands it.

Unfortunately, what these reasons sound like are lame reiterations of very old, tired , excuses for refusing to free the source, and even more unfortunately, they try their best to propagate old, easily-dismissed (but apparently, not so easy to put to rest) canards.