The new Javascript BikeTag API is reaching a stable state: https://npmjs.org/biketag
And can be used to start building/working with your own BikeTag Games! Please reach out if you have an interest in doing so and we'd be happy to help guide you through the process.
This API is still actively being developed and won't be suitable for production use until at least version 2.0.2.
Thanks! ~BikeTag Team~