Below is a bar chart of votes which I find helpful, constructed from data as I'm writing this. The figures are unlikely to change much at this point.
TensorFlow dominates, followed by Keras (which uses Theano or TensorFlow as its backend) and then Theano.
TensorFlow and Theano (on their own or via Keras) account for two thirds of all votes.
TensorFlow (78) ******************************************************************************
Keras (34) **********************************
Theano (20) ********************
Torch (16) ****************
Caffe (13) *************
DL4J (9) *********
CNTK (5) *****
MXNet (4) ****
Paddle (4) ****
DSSTNE (3) ***
Other (3) ***
H2O (2) **
Lasagne (2) **
Neon (2) **
Block (1) *
Chainer (1) *
Dali (1) *
Marvin (1) *
Veles (1) *