Battlefield 3/4

Hey. I didn't know whether to post this under BF3 or 4, but here goes. I installed and have been happily playing BF4, with punkbuster and everything, but my friend only has BF3. Well, he wanted to play, so I fired up battlefield 3 again, which on my computer, it was installed AFTER BF4, and it said that if I wanted to join a game, I would have to install punkbuster. I thought that was weird but I went ahead and clicked to install the plugin, but this time it took me to the evenbalance website, where I had to click on my operating system, and then wait for punkbuster to open up and "add" BF3. This was really strange, as I have never had to do this with punkbuster before. I can't even find it on my computer to go back to that "add game" interface to show you guys a screenshot. The instructions are on the website though. I guess my question is, am I okay doing this? I was a little weary, but avast said the site was fine and I was able to play the game just fine after I installed it, and my computer is currently running great as well. BF4 runs too, I just checked it, along with other games.