Funnily enough, Steam doesn’t have a rule about exact same names, here is their response:

“Hey there,

Valve respects the intellectual property rights of others, and we ask that everyone using our internet sites and services do the same. Anyone who believes that their work has been reproduced in one of our internet sites or services in a way that constitutes copyright infringement may notify Valve’s copyright agent using the form below.

That said, you may want to talk to the other developer directly to work out a solution. We don’t have any rules against games sharing the same name, so there wouldn’t be any problems for us if you and the other developer decided to name your product similarly.”