What exactly is pseudocode in this context? Is English text combined with math formulas considered pseudocode? What if it is highly suggestive of how it would be implemented?
And what if the pseudocode looks a lot like a real implementation (e.g., say in python)?
If you copy a compilable function and give attribution, probably no one will care. If you copy a whole enterprise system, they might. If the original author cares, there should be a rights notification in the code. In particular Wikipedia articles have the GNU Free Documentation license, so you are pretty safe there.
I would also rather not credit a Wikipedia article in my closed source software unless it's really necessary.
So the issue is whether an algorithm implementation is transformative when compared to the pseudocode.
The answer to your main question is fact specific. Each case is different and a court of law will look at the specific facts and make a ruling.
Talk to a lawyer for counsel that relates to your specific facts.