Allwinner has repeatedly violated the GPL (and by proxy so have most hardware manufacturers and resellers using or selling products based on Allwinner chipsets). Either by not providing (Linux/Android) kernel or u-boot source at all, or by delivering trees with pre-built binaries and no matching source code. They even blatantly use LGPL licensed code in their userspace libraries for media decoding.
Over time, Allwinner has only increased the binary blobs present in their kernel trees, showing clearly that - even though Allwinner in the meantime joined Linaro - it is not progressing. Quite the opposite actually, and one has to worry about what value Linaro membership really has if a member is allowed to behave like this. Allwinner also joined the Linux Foundation as of June 2015, while compliance issues clearly remain.