Installing a complete instance of the code is not nearly as difficult for the AO3 as it is for Dreamwidth. exor674 managed it in about an hour from a standing start. I agree it's not as easy as getting a Dreamhack or AO3 webdev - that's why we have support for junior coders available within the org, and have streamlined the Volunteers gateway hugely. But for an experienced coder who's going to submit more than one pull request, it's something they'll almost certainly do anyway, and would do on any other open source project apart from Dreamwidth, so I don't think it's unreasonable to expect as an alternative to filling in their name and email address on a form.