fwiw Heng Li was "the author." He was a postdoc under Durbin's professorship. I was around when bwa was developed and was working in a collaboration with Heng Li (I was working on SOLiD R&D). Any development emails were between Heng and our team, we never spoke with Durbin.

first author on a paper like this indicates the most significant contributions https://academic.oup.com/bioinformatics/article/25/14/1754/2...