The Ruby driver can save and retrieve a BSON Symbol if the saved document is modified via JVM langauges that wrap the Java driver, the Symbol would be replaced with a String.

To allow retrieving of Bson Symbols I would suggest this:

_put( name , new Symbol(v) );

I have patched and jar'ed my fork and my tests in JRuby do save and retrieve a Ruby Symbol.

I am not in a position to check the other JVM languages though, sorry.