The PlainADC library sounds great and it is worthy of praise based on the results you have posted.
That said, what coding I do, I do with the intention of publishing a finished product that others can independently replicate. If my code depends on a closed library under a license agreement or copyright, then every person wanting to use it is forced to go through this "may issue" bottleneck which raises barriers to their successful duplication of my results.
With that in mind, your retention of control over the PlainADC library, in my opinion excludes it as a candidate for inclusion in any project I am working on.
A simple google search allows you to track how the library is being used. Social media being what it is, in most cases the same level of social interaction can be pursued with the creator of projects you like.
I've identified an alternative path forward using CMSIS libraries to satisfy my requirements:http://arduino.cc/forum/index.php?PHPSE ... 107.0.html
I doubt I will dissuade you from your position but it just seems like a waste that otherwise excellent tutorials are not living up to their potential educational value in the cases where this release policy discourages students from following along.
In any case, thank you for what content you have released on your blog. It was one of my first introductions to DSP concepts.