Scratch

And this is resolved already... it's number 2 in Chrischb's sticky Suggestions that have been resolved already. I'll quote that bit:

Chrischb wrote:

2. Locking downloads

There isn't a sticky on this, but it was going to get here anyway.
This has been proposed several times (I only remember three or so instances of it, and there could have been more). It was cleared up each time...

Magnie wrote:

Scratch is open source this has been suggested multiple times, read the license (even though I havn't read it I already know the rules.) It will NEVER happen.

cheddargirl wrote:

But wouldn't the option to refuse download be against Scratch's motto to imagine, program, and share?

So it's been mentioned already. If locks appeared, the Share part of Scratch would be left behind. Cheddargirl stated what she would do:

cheddargirl wrote:

Honestly, if I didn't want other people taking the art and music form my projects, I would post my projects on my own personal site and set my own Creative Commons/copyright license or not upload my project to the Scratch website at all.

So you can go with that if you like.
And again, it's not going to happen.

One thing Chrischb forgot to mention: It'd go against remixing, which is strongly encouraged.