MP5 Machine Gun (Koch, Heckler, assault looking thingamabob)

[Innoventive Software, LLC]

I am on MAC and manually placed the pose file in the /Library/objects/actors (poses) folder, and placed the relationship file in Library/objects/actors(relationships) folder.

That is your problem. You need to download them to somewhere ELSE than FrameForge (like your desktop), making sure they maintain the same name as is shown on the forum, then IMPORT them using POSES->IMPORT and RELATIONSHIPS->IMPORT.

See the announcement at the head of the poses and relationships forum for more details.