There's the odd pirate reference here and there in Valve's DOTA 2, but that wasn't enough for this mod. No, the creators of the STS Pirate Language Pack wanted to essentially re-localise the game, so it could be understood by toothless nautical bandits of the 17th century.
Serving as a "complete rewrite of the entire language in Dota 2", the pack has, after two years of development and a test run last year, been released to the public and made available on the Steam Workshop. Why two years? Because it's a Steam-wide project for the services baked-in localisation, meaning that while a DOTA 2 patch is the first to hit the internet, there are more planned, with Team Fortress 2 next.
If you're in the DOTA 2 beta, you can try it out below.
STS Pirate Language Pack [Steam Workshop]