Sightly modified version of this captcha is being used there:
habrahabr.ru/core/captcha/
autokadabra.ru/core/captcha/
As these websites are with closed source code, their authors violate terms of General Public License.
PS: Message for guys, who made these websites (russian-only):
Мухахаха! Злой план! Я, порошочник96, делаю гадость хабру и никто этого не видит! Мухахаха!