@Alex Jordan says:

Agreed with Douglas WRT reproducability. Mostly the reason I care about reproducability is because it makes certain classes of attacks detectable. Since you're not executing free culture works, I don't see a problem.

Yes, I should address this! I'm talking about "building from source", but not "byte for byte reproducibility" a-la the Debian reproducibility project.

When I'm talking about "source", I mean the "preferrered form for modification", a-la GPLv3. Definitely vague, as has been pointed out, and why things are so vague, and whether or not things might solidify in a given domain, is a topic of interest for me. To see a good example of this (maybe the best example), see the Blender Open Movie Projects, which do release their complete and corresponding source... possibly sans some clear ways to rebuild.

So why might someone want source / preferred form for modification of a given project? Here are some reasons:

• An opportunity to learn. I've learned a lot by opening up the videos from the Blender Open Movie project files and playing around with them. It wouldn't be possible to do this just watching the rendered "binary" video.
• An opportunity to contribute. Free culture projects have seemingly failed here for a long time at building projects that can have a distributed team of participants. (Exploring why this was and another model of it was a primary goal of Liberated Pixel Cup.) I'd like to see more community-built larger art projects. There's a lot of components involved in there in not making things just a terrible hodgepodge, but it's possible to do.
• An opportunity to reuse, like a "library" of materials. There's a vague sense of this in the "remix culture" aspect of free culture arguments, but most of it is a pretty sad form of reuse, basically remixing the lossy final binary that you got from some source.
• Verification of reproducibility? So this is interesting, because the question is why one would want to do such a thing! It's mostly be asserted that one wouldn't! But what about reproducible science as an example of a domain where proving something seems important by reproducing research? But also, sometimes code and data are intertwined.

It's true that there's not as much of a strong need for the preferred form of modification in free culture, but free culture would be a much more interesting movement if there was more of it.