If I had to wage money on it, I'd say Gumbo is an early developing hen.
Some hens will have those little bumps were the roosters develop spurs. However, he/she does have somewhat of a rooster-like stance and what looks like to be almost-but-not-quite pointy feathers around the neck and saddle area, so there is also a possibility that Gumbo is an hemporphidite (sp?), which in human terms, means both male and female, but in chicken terms, pretty much means neither male or female (won't crow and won't lay eggs).
Even if it's a hen, you may not get eggs until next spring because the weather is cooling down. If it does end up a rooster, you should get crowing in the next couple of months.