they had an answer on ru.cc already, 3 and 4 weeks ago. it is pointless to add a channel in widget-like manner, because of specifics: all links leads to "download viber" page, but not to the channel itself. fully-functional integration would be against tou (smth about sending data to 3rd party). it is possible to create link to the channel (they have declined this option).
i have no idea why they are bringing it up here. i'd rather not participate in the thread: i don't feel like to repeat myself at 3rd time.