OpenUtau is an open source editing environment for UTAU community with modern user experience.
vBetaMIT
U
Utaformatix
oxygendioxide.utaformatix
Utaformatix (https://sdercolin.github.io/utaformatix3/) is an open source online singing synthesis project converter. It supports vocaloid, utau, deepvocal, cevio and synth-v. This is an electron app which lets you use it offline.