Before Sonar was released (early 00s) the full product name was Cakewalk Pro Audio (The company name was Twelve Tone Systems). I want to have a copy of it. So:

1. Is it legal to buy a 2nd hand version of Cakewalk Pro Audio?
2. Will it work?
3. Does anyone at this forum wants to sell it to me?

You can't buy a previously owned copy of Pro Audio. 

John
You can't buy a previously owned copy of Pro Audio. 

Why not?

Yes! If it's an unregistered version.

If its unregistered it wasn't previously owned. 

Why would you even want a copy of Pro Audio?

John
If its unregistered it wasn't previously owned. 

It could have been previously owned, but not registered...sitting in a pristine cellophane wrapper somewhere, lost in the mists of time...
 
Legend has it the Roman emperor Titus, after completing the colosseum, was so distressed by the effort it took and the death of his father than he never actually registered his copy of Cakewalk Pro Audio. It may still be in a museum somewhere.

Sarcasm, right?

wwwwwwwwww

John
You can't buy a previously owned copy of Pro Audio. 

Why not?

You must never have bought any version of Sonar to ask such a question. 

Cakewalk and Twelve Tone Systems before them did not and still not allow the resale of a software licence that has been registered. Transfers not allowed.

IF you can get an unregistered version then as Craig said yes go ahead and buy it. I know some who say they're still running it even though they have much more recent versions of Sonar.

Why do you want to?