Is the Wedding Song aka Trinkt le Chaim from Bernstein musical Modern 1.written by or is it a trad song as has Yiddish lyrics and 2.is score available to buy?

1. The Wedding Song, also known as Trink le Chaim, is a traditional Jewish folk song, and is not an original composition from Leonard Bernstein's operetta Candide or from musical "West Side Story"

2. As a traditional tune in the public domain there does not exist an official publisher but several arrangements in music stores in print or for download: https://www.sheetmusicplus.com/