Both https://trello.com/1/client.js and https://trello.com/1/client-unminified.js are back.
There were a few hours where client.js was not served from trello.com/1/, unfortunately. We are working on making changes to the way that it is generated and hosted and mistakenly pulled it from production. At the point in time we realized the mistake, we rolled back to the previous version so that everything was online again.