Question: Does "подруга" mean girlfriend as in "girl friend", ie a female friend, or as in "girlfriend", a romantic interest?

Doing a google image search for подруга seems to be getting matches for both types.

Answer: 
When the girl uses this word for another girl, it always means a female friend.
Used by man, it could have one of two values. Sometimes it's something between. But it definitely describes not-so-romantic relationships.
Can be any meaning depending upon context: one can use it when talking to others about his girlfriend.

When used by males has a connotation of long term relationship or a connotation of age of the couple (say 30+).