It means that the CD rom of an extinct language is like looking at an example of an extinct species which no longer exists in the modern world.

Dodoes existed in 1598 and became extinct in the 1600s. Because of their amusing appearance, particularly in the book "Alice in Wonderland," they have become a metaphor for extinction--particular for things that are recently extinct. There is a saying, "dead as the dodo," for anything fashion or custom or technology that is recently extinct or on the way to extinction. "Black-and-white film is dead as the dodo." Or I might say "Oh, I love black-and-white photography but maybe I am just an old dodo," meaning I am part of a nearly "extinct" generation. Dodoes lived for long enough for naturalists to collect them, stuff them, and put them into museums. In your passage, the metaphor is of someone studying a stuffed dodo in a museum and not realizing that the real dodo is extinct.

"A CD-ROM of an extinct language bears an uneasy resemblance to a stuffed dodo". It's a sentence from the book Spoken Here by Mark Abley and he is talking about endangered languages and minority languages.

Perhaps you can give me a context,or at least a full sentence.It could mean many things, I don't know what it refers to.