To complement the b2json script, I created a j2bson script. I needed this and couldn't find it anywhere. It is based on your latest version of b2json (including copyright, etc.) See attached.

Note that I was unable to fully round-trip by piping b2json -> j2bson -> etc because type information is lost. [I haven't messed around with hex editor's this much since the early 90s.]

Also, b2json has some typos (sorry for the paste, I'm fail at git):
diff --git a/bin/b2json b/bin/b2json
index 1a2dc5a..43c94bc 100755
— a/bin/b2json
+++ b/bin/b2json
@@ -40,10 +40,10 @@ end

1. print usage
   def usage()
   STDERR << <<END_OF_USAGE
   -usage: b2json.rb [-h] [file1 [file2]]
   +usage: b2json [-h] [file1 [file2]]

Converts a BSON file to JSON on STDOUT.

• You can pass multiple filename.
  + You can pass multiple filenames.
  If no filenames are passed, then STDIN is consumed.