When rundeck reads it, we get:

java.lang.IllegalArgumentException: Required property 'nodename' was not specified

Currently Foreman is exporting multiple hosts to rundeck using this format (but it looks like the single "-" between each host makes the YAML be interpreted as a sequence, and should not be there) :

--- 
  - 
    puppet.perimeterusa.com: 
      osVersion: "6.1" 
      osName: RedHat
      username: Admin User
      osArch: x86_64
      nodename: puppet.perimeterusa.com
  - 
    test.perimeterusa.com: 
      osVersion: "5.7" 
      osName: RedHat
      username: Admin User
      osArch: x86_64
      nodename: test.perimeterusa

This seems to work (with nothing in between):

--- 
    puppet.perimeterusa.com: 
      osVersion: "6.1" 
      osName: RedHat
      username: Admin User
      osArch: x86_64
      nodename: puppet.perimeterusa.com

    test.perimeterusa.com: 
      osVersion: "5.7" 
      osName: RedHat
      username: Admin User
      osArch: x86_64
      nodename: test.perimeterusa

This also seems to work (with "---" in between):

--- 
    puppet.perimeterusa.com: 
      osVersion: "6.1" 
      osName: RedHat
      username: Admin User
      osArch: x86_64
      nodename: puppet.perimeterusa.com
 ---
    test.perimeterusa.com: 
      osVersion: "5.7" 
      osName: RedHat
      username: Admin User
      osArch: x86_64
      nodename: test.perimeterusa

Other examples:
Current invalid export:
http://fpaste.org/OVr4/

Valid Examples:
http://fpaste.org/HpZA/
http://fpaste.org/OVr4/

According to ashp's chat history in #rundeck:
"...you have a sequence where you should have a map" (yaml related)

An that can be confirmed when I paste it in the website:
http://yaml-online-parser.appspot.com/
(select "canonical yaml" as output)