Thanks for your questions.
PWYM is designed to engage a wide range of interested musicians, from fans and novices to more intermediate and advanced engineers and producers. We're specifically focused on creating materials and experiences that have "low floors, wide walls and high ceilings." That's also why we called this course "Play With Your Music" rather than "Introduction to Advanced Audio Recording and Mastering." That's also why we provide approaches to critical listening and recording analysis in the first weeks so that PWYM participants can work with recordings and mixes they like.
The PWYM mix tools - http://sh.pwym.org/ and http://iye.pwym.org/ present mono mp3s for practical and educational reasons. The practical reasons are for download speed and protection of the high quality stems at the request of Peter Gabriel, who is quite generous is making these stems available to all of us for free. An educational reason is so that less experienced participants gain an understanding of the limitations of mp3s through working with them in the first part of the course.
In Modules 5 and 6, you will get access to 16-bit, 44.1kHz stereo WAV files within our custom Soundation.com online DAW. We've been able to acquire semi-dry stems for In Your Eyes which will be used for learning and applying audio FX to mix-minus-one mixes. By first working with mono mp3s in the first part of the course, we hope that participants will appreciate the differences in audio quality working with the CD quality WAV files in Modules 5 & 6. For the final remix project, you will get access to CD quality stereo stems for both Sledgehammer and In Your Eyes. Peter has agreed to allow PWYM participants - for free - to remix and share their mixes online and in our SoundCloud group for educational and non-commercial purposes.
In specific regards to Sledgehammer and In Your Eyes, it was a conscious, creative part of the engineering and production process (led by Peter Gabriel, Daniel Lanois, and Kevin Killen) to record takes directly to tape with printed effects. So, in many cases "dry" stem or multitrack recordings, especially from this era which were recorded to analog tape, simply do not exist, and perhaps never existed. Kevin Killen and Jerry Marotta shared a bit about that process in our live interview from last week.