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I'd like to check if a plugin has a callback or validator to the developer. Does anyone know what I should look for and in which part of the plugin?

I have looked for things like 'callback', 'valid' and 'email' but so far haven't seen anything. The plugin has a box in settings to fill in the license, but I guess it may not be checking. Reason I wish to know is that it is part of a monthly subscribe and if I stop I wish to know if plugin will cease, I'm also wondering if there is any way they will know the URL of my site as I don't wish to divulge.

Sorry about the title on this, I was having a problem posting this thread, tried 3 times and the title was meant to be with a question mark and read "How Do I Check …"