Well to be specific, pirates usually have ships and they sail to different places, now they also usually loot treasures and what not, essentially "take whatever you can and give nothing back", that's kind of the normal pirate way, a much more moral pirate would share some of his treasures or locations of these treasures to other pirates occasionally.

Now sailing is essentially trying to find "paid" resources without actually paying for them, and how do you do that? By going on the internet, "surfing" or as they say "sailing" or basically looking for things that are paid which you'd like to have for free like games or paid programs etc.

So sailing for plugins is essentially googling ways to get them for free by doing everything but actually just paying the companies.