Nope. germ.io is not a mind map. But boy, does it look a lot like one (especially when you're thinking up a creative idea and planning a project around it)!
Mindmaps don't constrain structure:
The biggest problem with mind maps is all those fuzzy connections. While that works great for something like building a sitemap of a website, when it comes to solving a problem or building an idea, you want to focus on one idea at a time and break it down.
The greatest ability in a mindmap (to connect random/ disparate nodes together) is it's biggest problems. germ.io solves this by forcing you to think through just one node (or idea) at a time, and break that down hierarchically. That way, every node has just one parent - one bigger idea that broke down to give you your current node. There is always context at every step.
Mindmaps constrain content:
The bigger problem though is Mindmaps inherently are not about filling up details into each node. When you come up with an idea, you just want a place to pour down your thoughts in as much detail as you want - not worry about the structure and connections yet.
germ.io offers a free-form editing experience so you can throw down your idea and explain it the way you want.
germ is built on the theory of MECE - progressively breaking an idea in Mutually Exclusive, Collectively Exhaustive sub-parts. As a result, once you break down your idea, making your germs actionable and building an execution plan from it becomes easy.