After some examination of WiFi traffic, I found the core problem and built some code to prove the hypothesis.   The core issue is that the SkyView system doesn't send a 'heartbeat' message as outlined in the GDL90 protocol description; it only sends 'traffic report' and 'uplink' messages.    The solution was to build some code on a small embedded device that receives the wifi messages from Dynon and forwards them, unchanged, to the IFD.   Additionally, this device sends a heartbeat message once per second in accordance with the GDL90 specification.    The result is traffic and weather from my Dynon system was displayed on my IFD540 without issue.   There is no evidence of any kind of "enhanced" or "extended" GDL90 being produced by the Dynon system - it's just missing some of the required items.

The heartbeat message is important to the integrity of the system; something that simply relies on the presence of traffic (or uplink) reports cannot differentiate between no traffic (or uplink) reports and a failed sensor.   The heartbeat message makes that differentiation possible, and it would appear Avidyne has the correct implementation in this case.

I have been in touch with Dynon on this issue, but if this is something that affects you and you'd like to get traffic and weather from your SkyView system displayed on your IFD, contact Dynon and reference the above information.   Their product manager is aware of the issue and likely just needs to know that it's a feature desired by their customers.