I don't think Joel's conservative approach was all that bad.
He made a judgment call for --his-- company's products at the time. He could afford to, and it appeared to have worked well for his product line. And believe it or not, people wanted to work at Fog Creek.
In 2006, I wouldn't have imagined the explosion of language acceptability that we have today. We see everything from Ruby, Erlang, Scala and other languages widely used -- a great thing that you can use the best language for software development instead of being limited to the "safe enterprise" choices of Java or Microsoft .NET.