Not a lawyer, but if the software project had an independent owner for its trademark, I believe that they'd have a case against 10gen. The name is deliberately chosen to provoke confusion between the two.
Their previous full name was "10gen: the MongoDB Company"; they've been trying to dispel confusion over the company name vs. product for a long time (probably since they pivoted towards making Mongo the main business product - 10gen started as a PaaS company).
source: worked there
Edit: the title of this submission should really be "10gen: the MongoDB Company shortens their name to MongoDB, Inc." Less attention-grabby, more truthy.