First of all as most said, OSS and piracy are not related. This thought lurks in the mind because of a fundamental misunderstanding: GNU/Linux (others etc.) is a free ALTERNATIVE to Windows (or paid stuff). OSS and GNU/Linux are NOT ALTERNATIVES to paid software.
Why do I use Linux? Coz I can't afford Windows and I do not want to pirate Windows? No! I use Linux coz I want to and I also use Windows (fyi a legal version) coz again I want to.
If you wanna put forth the analogy that Linux is a free alternative to Windows and people use if only due to that reason then wouldn't it be correct to say OSS users are pirates? I mean, the thinking leads to something like this: OSS users can't buy Windows, so they use free GNU/Linux distros; since they can't buy Windows they won't buy songs, so won't this analogy make them natural pirates???? Hence, this relation is flawed.
Do you think copyright infringement doesn't happen in OSS? Many a times, GPL'd stuff is taken, modified and released under someone's name. So an OSS doesn't come with a bond that you need to adhere to all copyrights otherwise you'd be hanged. There haf been lotsa cases like these.
Secondly, it is a big mistake that OSS = Linux! People say ANi (infra) is an OSS user coz he uses Ubuntu. Correct. But nobody says Ashwin (drgrudge) is an OSS user, but he's Mac user (which is also partly correct). Why? He uses VLC, Adium etc. Doesn't that make him an OSS user? So we need to clear some basic concepts. Who is an OSS user, is OSS an alternative to Windows (and paid software?) Are OSS and piracy related?
Charan, its like saying: Dude, you are an OSS user; so you can't zerox a portion of a novel. Now isn't zeroxing a part of novel also piracy? Why is this not taken into a/c? Just coz its not related to computers? So from the title it is implied that if you are an OSS user you should lead an ideal life, obey all rules, never give bribes (again, isn't it against the laws just like piracy?).
Now I dunno if its piracy but recently I bought an OSO cd and put the ripped music in my cellphone. If it is, then I'm a pirate.
Oh yes, one thing I'm sure of which I pirated (and the only thing I pirated) was downloading a pre-dvd rip of Transformers many months which I am yet to see!!! (yes, believe it or not I've still not seen Transformers).
Other than this I haf not pirated anything. But then you can't say hey I haf only one pirated movie which I've not even seen and dunno if I'll see it. Ther is no "degree" of piracy. A pirate is a pirate. So whether I watch it or delete it without watching, I've downloaded it; so I pirated it.
I goto theater to watch movies; I don't listen to music much other than soothing instrumentals (which I buy and rip, so prolly I'm a pirate again). If I like a movie, I buy the DVD (Thanks for moserbaer

).
To answer your question in my words:
Do OSS users infringe other copyrights
Yes, I do. I pirate by zeroxing parts of text books during my exams, I break laws by somtimes by jumping signals, I haf the legally bought-ripped OSO songs and instrumentals on my cellphone, I haf Transformers pre-DVD "downloaded" rip on my HDD. So do I infringe other copyrights? YES.
Is is correct for "OSS Users" to infringe other copyrights? YOU DECIDE IT AFTER READING MY REPLY ABOVE.
PS: Charan, No Flash on my PC. I go there to work on it. And I'm trying out Quanta now. I know you'd ask about it, so clarifying here