I wrote them yesterday, that's what the support answered:
Thank you for contacting Xiaomi Customer Support. I am xxxx and understand that you want the GPL source for the Mi Router model AC 2100.
I am sorry to inform you that as of now we are not selling our devices through our Global website, so we won't be able to assure you regarding the link. However, would request you to visit our website for more information: http://www.mi.com/en/ and our Facebook page https://www.facebook.com/xiaomiglobal for more updates. Also, Xiaomi does not provide international shipping.
For any further queries, feel free to contact us.
Regards,
xxxx
Xiaomi Customer Support