It is if you recognize it as a Burmese and take it knowing that you aren't prepared to deal with it. Personally I would bring it home, but only because I have two empty 8'x30" enclosures at the moment that are already set up with heat and t-stats, so it would have an appropriate place to live. If after a few months of working with it I figured that it wasn't going to work out, I could find an experienced keeper for it.
IMO the seller is the wildly irresponsible party in this transaction for advertising a Burmese as a ball python.