I have no interest in using them for nothing, because I normally use RK clean SDK.
According to JXD "dev", this SDK is compatible with both 7300C and 7800B and use Android 4.4.4. No idea, I have not even downloaded. But I share it here in case someone is interested in development for these devices. You can also check with Lujji's kernel to see differences and check if it's compatible with 7800B.
I will only have these files in my mega account for one week. So I suggest if someone download it share a mirror for it, because this files are huge and I don't have too much space available in my account. Don't blame if these files are not available after a week, because I won't upload them again.
also, I am only sharing this. I am not assisting or helping JXD 7800B development to any extent. There is a lot of information in forums to begin development for RK3188. Also, my github account can be used as a reference for kernel.
Good luck with development.
Download: