OpenSFX being distributed under CCSP+ 1.0, does that mean that it will NOT be included with a future Debian distro?
Yes-ish. It won't be in main for sure, although there might a chance it will be included in 'non-free', but 'non-free' is not really part of Debian; most packages in there are just for support, e.g. the ATI video card driver.
If that is not the case, then I fail to see why it now matters with offering the same license for the music files.
The whole 'does not show in Debian' issue is why I dislike CCSP+ 1.0, even for OpenSFX. However, if the only source of material is a CCSP+ 1.0 licensed databank of samples then you have to use that license, or not package it and thus not finish OpenSFX. So I decided that a finished OpenSFX that could not be sold is worth more for our users than an OpenSFX which was fully free and people could sell.
As it seems you are going to compose it yourself, or have good contact with the composers, licensing it under a freeer license would be better from a point of usefulness in Debian and its derivatives (and possibly other distributions).
MIDI files are not pre-recorded, it is a digital form of sheet music that is performed on-demand by a synthesizer, at the request of an individual, and thus is a public performance. In most of the cases with the MIDI files we'll be using, the composer and publisher is going to be the same individual. This is what GPL doesn't touch, and what many composers gets antsy about.
Doesn't GPL touch that? The MIDI files would be the "source", the MIDI synthesizer is the "compiler" and the result of that would be the "application". In this case packaging the sound ("application") means that you need to add the license. Any modifications to it means that those modifications need to be clearly marked. So in fact it might be a quite strong license for MIDI files.
For example if someone uses the music for a movie that movie has to be GPL because it has been incorporated and as such that *if* you get the movie you have to get the sources of the movie which you then can distribute under GPL. This basically makes the music unuseable commercially (due to the licensing), which means that they have to ask the author of the song that can be found in the readme/copyright files for a relicense for their purposes (possibly with payment).