They're both implementations of the MVC pattern, but short of that there seem to be very few similarities between them. Admittedly, I've only built one project in RoR, but the framework itself required much less configuration and Ruby is a huge departure from the Java/C# coding style.

The MVC design pattern has been in use since 1979; it's nothing new. It's also worth noting that Java devs and Microsoft devs were building MVP (a modified version of MVC) based apps in the 90's.

I'm not trying to dis RoR, because it seems like a pretty solid framework and nobody can deny that the 37signals guys were the motivating force behind the current wave of MVC development. However, what they created was a better web implementation of an existing pattern and I honestly think Django and CakePHP are much more obvious imitations.

Finally, it's worth noting that the ASP.NET MVC framework is open source and has similar license to RoR.