If it's from another distro I trust enough, not always. (Yes, I will frequently pull the repository of the packaging system for another distro, rather than pull from Github or whatever else.)
I'm also going to replace "compiling" with "running", because a lot of software I run that's not in my distro is in Python.
If I otherwise have to grab it from some other source, then I mostly read it through. If I just need a subset of it and reading all of it seems like too much of a hassle, I'll grab & use the part I need and ignore the rest.
Sometimes I'll just reimplement that part in some other language instead because I don't feel like bothering with the upstream's and don't need all of it.
