The plugin is fully compatible with the i18n standard that WordPress uses. This means that you can translate the plugin using po/mo files.
The text-domain for the CORE version is digital-license-manager and the text domain for the PRO version is digital-license-manager-pro.
Since the CORE version is used in the PRO version you will need to translate the CORE as well if using the PRO version as well.
Which software to use for i18n?
You can use any, really. It doesn’t matter as long as it supports .po/.mo generation and the i18n standard.
We can recommend the following: