I think "accessible to everyone" also means,
* No NDA required
Usually, to purchase a new architecture processor like this requires signing an NDA.
But, Parallella doesn't require any NDA.
You can buy Parallella boards anytime if you want to, no matter who you are.
Also you can get Epiphany SDK, example source code, reference manual, board schematics, HDL source code, etc., for free!
* Low cost
Usually, these development boards are priced over $10,000.
But, Parallella board is only $99, so, even poor people like me and young people can afford to buy it.
Certainly you can do parallel programming on your normal PC, but the difference is architecture.
PC's CPU has 2 to 8 cores, Epiphany has 16 to 64 cores for now.
Epiphany's architecture is very "special" one, like a future super computer node.