I found this project while looking for a way to renew my SSL certificate without having to use certbot which has a lot of dependencies including python. This program is really small and simple and does exactly what I need. It's perfect.
If you like minimal dependencies another one to take a peek at may be acme.sh [1]. It depends on bash, openssl and curl. It seems to work fine in ash as well. It has code to handle most API's and most importantly to me is the great documentation.
In the same spirit of minimal and light weight there is also testssh.sh [2] for testing TLS on HTTPS/SMTPS servers that also depends on bash and openssl.