I haven't looked recently, but at one point I did a survey of rotation matrix examples online and the vast majority of them were wrong, with subtle typographic errors in a sign on a term here, or a cosine swapped with a sine operation there. I've seen "game rendering loop"s that leak memory every frame (in C++) or allocate every frame and eventually cause GC (Java, C#, JavaScript). I've seen OpenGL initialization snippets that didn't account for pixel density of the display properly and ended up rendering at too low of a resolution.
No, don't paste snippets of anything you find online. It's likely to be really bad.
You can easily tank the framerate if you account for this. At best, it should be an option in the video settings (if you're going to have them).
What's so difficult about linking against a lib/including some headers and pasting the code snippets? The only part I really had problems with was figuring out that I needed glew, and why it wouldn't work on osx with the core profile .