[thEsp]

I'm addicting to editing/re-viewing AMXX modules, it's just fascinating! Anyhow, I came here to ask two main/easy questions.

In most of (if not all) projects and their source codes, I noticed that authors wrote a license. But I'm really not getting what it is supposed to be, a mark that module is free/open for all or anything related to copyright laws (etc.)?
Second, I'm really confused of HLSDK/MM, should I only use header(s) I need or every of them?

Thanks.