Yes, the main purpose of Anarki is as a place for people to share the work they've done on/for arc. Since arc itself is easily modified, a lot of the code on Anarki actually changes the language. There is also a fair amount of library developed there as well, though since most important library functions can be lifted from Racket that's not so much of an issue.
However, beyond simple bug fixes pg hasn't ever discussed much about changing the language itself with the community. As far as I know, none of even the truly good, simplifying and useful features of Anarki are planned to be lifted to arc.
