Kaldi is a toolkit for speech recognition written in C++ and licensed under the Apache License v2.0. Kaldi is intended for use by speech recognition researchers.
It’s being used in voice-related applications mostly for speech recognition but also for other tasks — like speaker recognition and speaker diarisation. The toolkit is already pretty old (around 7 years old) but is still constantly updated and further developed by a pretty large community. Kaldi is widely adopted both in Academia (400+ citations in 2015) and industry. Kaldi is written mainly in C/C++, but the toolkit is wrapped with Bash and Python scripts.
Voximal embedded several connectors to use the kaldi engine.