Consider king-of-the-hill challenges. Significant effort on the part of the challenge presenter goes into collecting the code entries and massaging them into a runnable state (language versions, compiling, etc). This effort can be reduced by limiting languages, but that also limits your audience.
To quote from the tag wiki:
In fact, it is strongly recommended that before posting you upload the test framework, one or two simple example bots, and a build script as a public repository on a site such as GitHub. Then competitors can easily download and build the other bots when developing a new one, and might even send you a pull request with their new bot and its build script. See, for example, https://github.com/pjt33/ppcg36515 , which has a make setup that allows building the test framework and the bots in one step.
There is certainly nothing wrong with requesting that competitors send you a pull request, although I don't think it should be an absolute requirement to create an account on a separate system and learn how to use git to participate.
Is it wrong to ask for an executable for languages that compile?
There are various practical problems with this.
- Multiple platforms (x86 vs x64 vs ARM, Linux vs Windows vs OS X, etc.)
- Source code can normally be copied directly; binaries need to be encoded in some form, and it may be as much hassle to install
uudecode on Windows as to install a compiler.
- Running an executable file you downloaded from the Internet requires putting a lot of trust in the person who posted it and the various systems through which it has passed.
These day's it's simple to stand up serverless services. Is it wrong to ask for a web service endpoint?
It may be simple, but it's not necessarily free, and it's still a big learning curve for people who don't already do it on a regular basis. And that's before you get into the many different flavours of web service, which may mean that calling someone else's is more difficult than compiling their code. I would strongly recommend against this.