It's not a bad name. The point is it's a name of a very well established, years old open source project used as the near-universal interface points between web servers and Ruby web frameworks.
It is also the name for physical pieces of metal in which you place servers to store them while they are online.
I don't see a problem with two items have the same name provided the functionality they provide is substantially different. Nobody is going to get confused over whether they are referring to the PaaS application or a Ruby library in everyday conversation.
Wow three whole years ago? Pack it up ladies and gentlemen we're heading to the Ruby funeral. Sorry for the snark, but tens of thousands of developers are using the real Rack every day. It's a mature component in widely used web frameworks.
Next up a JavaScript framework called Rake because who uses Ruby anymore.
We picked Rack because we like the conceptual analogy. The naming conflict is unfortunate but there are a limited set of good words available. We hope that context will make the meaning clear.
Seems like this is likely to reflect something other than changes in language popularity. Frankly the data doesn't seem very interesting without correcting for other factors such as total volume of jobs.
Overall, Ruby looks pretty much as popular today as 3 years ago to me from that data, though perhaps with Rails in a downwards trend (awesome - I love Ruby, but finding Ruby work that doesn't imply Rails is harder, and I don't like Rails).
But it's besides the point anyway. I simply explained why someone mentioned Rack, I don't particularly care either way (probably because I don't really care about Convox Rack - I'd never use a single vendor solution like this, and haven't exactly hidden how overpriced I find AWS in past comments).
I don't see a problem with two items have the same name provided the functionality they provide is substantially different. Nobody is going to get confused over whether they are referring to the PaaS application or a Ruby library in everyday conversation.