If you are trying to run a rails app from 2005 your biggest issue is the trillion security holes in your app and not getting it running which is usually not too hard.
That is absolutely true, and probably equally true for any other web application that was wasn't maintained for 10-15 years. But this is article is talking about the ability to run older applications, not about safety concerns about doing so.
I just wanted to point out that, while Rails is far from perfect, from a software-archeological perspective there's not really much ground to pick on it. The ruby gem ecosystem (again not perfect) is at least pretty stable in the sense that 10+ year old libraries are readily accessible (as they should be!).
