According to Humble Bundle, cannot be redeemed in these countries:

AD AL AM AT AX AZ BA BE BG
BN BQ BR BY CH CN CS CY CZ
DE DK EE ES FI FK FO FR GB
GE GF GG GI GL GP GR GS HK
HR HU ID IE IM IO IS IT JE
JP KG KH KP KR KY KZ LA LI
LT LU LV MC MD MK MO MQ MS
MT MY NC NL NO PF PH PL PT
RE RO RU SE SG SH SI SJ SK
SM TC TH TJ TM TR TW UA UZ
VA VN XK YT