During literature review for my research proposal, I have come across a professor who has published several papers in my field, some closely related to the topic of my own research. In a series of papers he uses a specific model, expanding on and extending it in each paper. In my work, I want to use the same kind of model (evolutionary) and I would love to see the source code, both to better understand and replicate the results and because it would tremendously help me in getting started. Unfortunately, I could not find it anywhere and it is not published with any of the papers.
I am wondering if and how I should ask for the code and have three related questions:
Is it common to just email and ask for the source code or would that be considered somehow inappropriate? I might well end up applying to the university that professor is teaching at, so I don't want to leave a bad impression.
Who is the appropriate person to contact? All of the papers on the model have been published by by the professor and the same two co-authors, some with additional co-authors. Should I email the professor himself, one of the co-authors, or all of them?
How much detail about my own research should I include in my email? Just what's sufficient to justify the request or more, possibly a draft of the proposal?