If you like Java, have an interest in homebrew game development on limited restricted platforms, and would love to see your game run on these game consoles, then Blu-ray Disc Java (BD-J) is exactly what you want!
No. Absolutely no modding or hacking is necessary to run Blu-Play games. The consoles were designed for this!
(There is an advantage in owning a jailbroken PS3 though, because it lets you run Blu-Play games from harddisk, which means you don't need to burn a disc. But that is not related specifically to Blu-Play).
No. Anyone can write a Blu-Play game. And you are encouraged to use the Blu-Play logo for any Blu-ray Disc Java game you make.
If you wish to use the Blu-ray Disc logo though, then you need to sign a Logo License Agreement (LLA) with The Blu-ray Disc Association. But there's really no need to have the Blu-ray Disc logo on your disc. If you absolutely feel the need to indicate that it's a Blu-ray disc, then you are allowed to put "Blu-ray Disc TM". More info
Apart from Java programming skills, you need the BDJ.jar file to compile against. This BDJ.jar file has been put together by multiple Java stubs from different companies. Proper protocol dictates that you're supposed to download these stubs from various sites, and create your own BDJ.jar file. Unfortunately this is no longer possible, because many of the stubs seems to have vanished from the Internet over the years.
Tom has managed to find some of them in newer times, and he wrote a guide here on how to obtain them. But 3 of them are still missing.
Luckily the BDJ.jar file can be obtained from other places as well, such as the Minimal SDK from the tools and links section. It can also be found bundled with software media players such as PowerDVD.
No. It is your property, and you can do with it as you see fit. Just as if you had recorded your guitar skills on a CD. Or if you were a wedding photographer selling your work on a DVD or Blu-ray Disc.
Well, you need to pay for whatever books you wanna study, and whatever equipment you want.
In short: All platforms that feature a Blu-ray player. See Platforms for a detailed overview.
Check the links in the tools and links section. Visit the community forum. Join the chat.
For jailbroken consoles you can dive into native homebrew.