I don't post heavily on those stuff but yeah you can find tons of them
for avmplus you have many sources
for more details you can also check out
The good news (even if no official statement from Adobe) is that from the "tamarin" project considered abandoned, it seems Adobe decided to revive lightly the project under the name "avmplus" and update the project sources with some changes they did recently; pretty god for Redtamarin as we are based out of the tamarin/avmplus sources code.
And yeah looking at those sources you can learn a lot about the internals and other details of "how things are supposed to work".
Some sources are not documented and I try to document them in Redtamarin, like
flash.trace.Trace for ex.
So yeah it is pretty interesting to get to see the sources of WebkitAIR, but this project imho is more something you would use to merge a browser with something like Redtamarin and does not really help for a browser ANE.
That said, there are a lot of concepts that could be reused later, like for example make the AS3 classes available in the context of browser.
Ideally, if enough people were contributing/sharing/communicating code we could perfectly imagine merging projects like AVMplus, WebkitAIR and CrossBridge, but unlikely to happen imho.
Also, as a side note, I do try to document (when time allows it) some of those undocumented or more obscur ways of working with AS3 things in the as3lang ActionScript 3 wiki, everyone is welcome to contribute.
For example, I put a but of stuff on the goto keyword, but documenting JSON reviver etc. could be interesting too.