It's been around for a year or so. I was wondering when it'd make it to HN. It's very nicely done but unfortunately the only implementations are in javascript.
If you want to make a library with a C compatible API I'd be tempted to explore SubstrateVM. It can export C symbols to the generated standalone .so / .dll files, maybe you can even reuse some of the JS code, or failing that, a Java/Kotlin implementation would be compiled down to native code or be usable from other scripting languages like Ruby.
Where are you getting 4 years from?
Check out the first commit: https://github.com/datproject/dat/tree/464679267049899eafa34...
Bit more on the funding history, etc. : https://blog.datproject.org/2017/09/15/dat-funding-history/