What Does Blazeds Livecycle Data Services Do, That Something Like Pyamf or Rubyamf Not Do

What does BlazeDS Livecycle Data Services do, that something like PyAMF or RubyAMF not do?

Other than NIO (RTMP) channels, LCDS include also the "data management" features.

Using this feature, you basically implement, in an ActionScript class, a CRUD-like interface defined by LCDS, and you get:

automatic progressive list loading (large lists/datagrids loads while scrolling)
automatic crud management (you get object locally in flash, modify it, send it back and DB will get updated automatically)
feature for conflict resolution (if multiple user try to updated the same record at the same time)
if I remember well, also some improved integration with the LiveCycle ES workflow engine

IMO, it can be very fast to develop this way, but only if you have only basic requirements and a simple architecture (forget SOA, that otherwise works so well with Flex). I'm fine with BlazeDS.

data push using django

I haven't done it, and it looks difficult.

What does BlazeDS Livecycle Data Services do, that something like PyAMF or RubyAMF not do?

PyAMF gives you the tools to send and receive AMF messages in Python.

But Django isn't suited to push, as normally for push you'd use socket connections rather than HTTP.

Which probably means having a Twisted server as well. You could still use Django... you'd maybe have signals code in your models telling the Twisted server to send a message back to the Flex client.

You'd still have to write all the data-binding type code yourself on the Flex side, though PyAMF provide example client code to get you started.

Apparently the Java frameworks for Flex do code generation for both sides, making it all much easier.

Remoting , Messaging and Data Management in Flex?

Though my answer may not be complete, it'll give you some hints.

Flash Remoting is a way of doing RPC using AMF protocol. Basicly you implement some server-side services with some methods, call them from your flex application and receive the result (using RemoteObject). Zend AMF definitely supports this.

The Message Service provides a complete publish/subscribe infrastructure allowing Flex clients and the server to exchange messages in real time. (from Wikipedia article on BlazeDS). I believe, it's mostly a Java thing, and is used for distributing messages across several clients. Making a chat is a good example of it's usage.

Data management is a set of features provided by LCDS (Live Cycle Data Services), which eases the development of CRUD. More info you can find in asnwers to this question.

It's likely Zend AMF doesn't support the latter two features, though I'm not sure.

What Does Blazeds Livecycle Data Services Do, That Something Like Pyamf or Rubyamf Not Do