There is an article by Brad McGehee at http://www.sqlservercentral.com/articles/Editorial/66637/%5B/url%5D (Online T-SQL Scripts and Copyright) which discusses exactly the issue you're asking about.
You might find helpful answers in the article or in the discussion ( http://www.sqlservercentral.com/Forums/Topic700079-263-2.aspx%5B/url%5D).
From my personal point of view a person who's responsible for SQL code (especially in production environment)
has to know (or at least should know) how the code he/she implemented works and why it works the way it does.
Assuming this, the person in charge most probably would have come to the solution based on internet code snippets sooner or later by him/herself.
By using the internet the solution might be available faster (depending on how long it took to find it vs. write it on your own).
This would be benefitial for the company since you can get more stuff done than without the internet.
On the other side, 3rd party code (what I consider internet source code belongs to) takes more time to be checked and tested than the code written by yourself since you need to get familiar with it.
The more complex the code gets the longer it will take to understand and modify it.
So, I think, -aside of the copyright issue- the answer is "It depends".
I, personally, do use code snippets from the internet to get some ideas on how to solve problems I'm confronted with.
However, those code snippets will not show up in production. I always rewrite the code.
I also do keep personal records where I got the idea from (usually a link to the related url).
If the code is marked as GNU/LPGL I might even add the link to the final/productive proc.
A pessimist is an optimist with experience.
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