July 28, aka tomorrow! In Europe at least, not sure if this also includes North America as well.

http://blog.eu.playstation.com/2010/07/27/introducing-earthworm-jim-hd/

I don't know why I was always under the impression that there is/was a PC version, looks like there might not be.

I just bought it of the USA PSN. The game is an amazing. It has been long time since I have played it.