My personal take on this is that the legal issues are important to consider in order to protect yourself, but I am less inclined to worry about the ethical issues.
If you want to use music downloads as the analogy, then what you are doing amounts more to "sampling" than file-sharing. You are taking little bits and pieces of what you have learned from different styles and including them within your chosen style as a way to better communicate your style - like a rapper grabs a discernabel piece of music and uses it as an identifieable piece of cultuiral context - most sampling is intended to pay homage and/or parody to its source.
I think the analogy breaks down once you think about it further. The music industry is based on content. Trading in that content hurts the bottom line for the artist who created it.
Martial Arts training and the industry around it are less about content, in my mind. Every style out there is derivative from other styles and the history of Tang Soo Do is murky, at best, anyway. Many of the commercial dojos or dojangs are actually marketing some bastardized American form of several styles combined, and / or re-packaging martial arts as excercise.
Most of the "pure" practitioners are "passing on" martial arts as a labor of love and either breaking even or losing money, either way making their living off of a parallel career.
To me, a more appropriate way to think about Martial Arts is to compare it to the Open Source movement for software. There, the ethical rules are that you can use the code as long as you are willing to share how you improved it and make it open to the next person to do the same. Also, you can't profit from it or lock it down as you alter it (you can't copyright it, basically).
I think the ethical consideration that is more sensitive is disclosing potentially harmful information (such as strike points) without the context and control of the dojang. Clearly, that is not happening with Hyung, since most of the application is locked away for interpretation.
All of the above is opinion, and I'm sure it could be argued the other way, but I think most martial artists have been financially successful on charisma as opposed to content, and I think most associations and practitioners are behaving more in line with the Open Source movement than with the copyright model of the music industry...
Thanks,
Jason