If you need to create your own fields in ACF and those fields are based on "PRO" types (e.g. "Repeater", "Gallery", etc), then you need to purchase a license for this plugin. Custom fields of basic types (e.g. "Text", "Image", "Checkbox") are not locked and can be used without purchasing "PRO" license.
Hello! ACF Pro is a plugin that comes bundled with the theme to make certain theme-related features to be working. It doesn't come with a license key as in accordance with Envato Bundled Plugins Policy: https://help.market.envato.com/hc/en-us/articles/213762463-Bundled-Plugins
If you need to modify/delete the existing custom fields that are used in the theme, you can do this in PHP code in this file:
If you need to create your own fields in ACF and those fields are based on "PRO" types (e.g. "Repeater", "Gallery", etc), then you need to purchase a license for this plugin. Custom fields of basic types (e.g. "Text", "Image", "Checkbox") are not locked and can be used without purchasing "PRO" license.