I seen it on a few.
Usually the js contains a small math question which gets solved by the js and inserted to a cookie.
And if you ask again with this valid cookie, you can pass.
Here a picture that explains it a bit better
To handle it with Openbullet:
Usually the most stuff is static, put it to a
your code here
END SCRIPT -> VARS "cookie"
And then you should get the value of the cookie which you can use for a 2nd request.