DVD is just a package you include in your isntall
No mind reading or arcane ceremonies. You install it, your DVD players suddenly work beyond the initial 20 second teaser.
Now, the legality of that package is up for debate depending on your location. US and similar patent recognizing markets; illegal.
The legal way is to use a program which includes the DVD codecs and pays the patent holder the required fees. LinDVD is the program normally used as an example. It's available at a reasonable cost and legally plays your DVD without requiring a comp sci degree to operate. (They also make the WinDVD everybody loves so much.)
I wouldn't foresee Blueray being any different; if you've got a reader then it's only a different codec that needs to understand the decryption process. I'd recommend looking for the legal method of playing them though but that's your personal decision.