UTM和MGRS到纬度/经度转换源代码？

What open-source / public domain software is there "out there" for conversion between Latitude/Longitude, UTM (Universal Transform Mercator) and MGRS (Military Grid Reference System)? We're using a VB6 library at the moment and would prefer to use something in another language and with a longer pedigree.What open-source / public domain software is th