Now Gnash is part Adobe Flash's rich developer ecosystem ...

The page, "the Truth about Flash", claims:

Finally, the Flash Platform has a rich developer ecosystem of both open and proprietary tools and technologies, including developer IDEs and environments such as FDT, IntelliJ, and haXe; open source runtimes such as Gnash; and open source video servers such as Red5.
[2010-05-17]

As another Gnash developer, Bastiaan Jacques, wrote on the Gnash mailing list, "Apparently it is sufficient to mention a partial implementation (that does not even support AVM2)."

Moreover, it's an implementation that was created with no help from Adobe:

• The SWF file specifications were reverse engineered by others and implemented in Gnash before Adobe published them.
• AMF and RTMP were described and implemented elsewhere before Adobe published the specifications.
• There are still no proper specifications for the older AVM1, which was reverse engineered for Gnash.
• While ECMA script - the basis of ActionScript 3 - has a free implementation, the entire proprietary Flash player API lacks technical documentation.
• Adobe uses patent-encumbered codecs such as H.264 and AAC that hinder the distribution of Gnash in some countries.

Neither should we forget that rtmpget received a takedown notice from Adobe for implementing part of the Flash specifications.