It wouldn't be a problem for me to pay the 0.5BTC, just get in touch with the founder of rollin.io for the API and if everything's ready to be done just tell me i'll pay and then you'll start the work

Also, sorry for my English, it's not the best but it's all I can do, I'm still learning it.

#Edit: Will send BTC in less than a week then you'll be able to start working on it