Skip the rest of my answers if you do not care about how this confusion came about.
Well, now I can't skip...
Etoys' UI is completely independent from the platform.
Ok. We did have those nasty problems with Universal Access interfering with other modifiers of mouse behaviors however. This was hard to track down and took a lot of time, but not related to Etoys of course. In that process I tested drag and drop of tiles in Etoys so many times (without wanting to actually program anything in Etoys, the children where doing that) that I was not thinking about the possibility of different types of tiles with different drop behaviors. So when I returned to the problems months later I was careless and did not think at all about different behaviors, just tested the drops and seeing that there was no drop zone and no embedding, totally ignoring the logic of the interface. And then I wrote tis post, thinking it still that same Universal Access problem.
Not sure what you mean by Universal Access interfere (something like lockable Shift key?)
One could argue that a plain expression could be dropped onto a script editor, and the user could expand it into a meaningful statement afterwards. But current system is not flexible enough to allow this.
-- Yoshiki