What does it mean to 'master' a language?

'Mastering' a language is very subjective. There is no benchmark for 'mastering' a language ... and yes, I do believe that certifications can be very misleading and at best are considered a very 'rough' gauge. Since technology changes at a very rapid pace, certifications are merely a gauge of obsolete studies.

Walter, I agree with your thoughts regarding new projects. I would contract someone who feels comfortable with a given language and learn from their work.