libbtc is a portable, pure C implementation of the bitcoin core methods provided as a re-entrant linkable library with a solid API, allowing you to write native speed custom bitcoin applications in any language which supports C bindings.
Linux, FreeBSD, OpenBSD, Mac OS X, iOS, MinGW.
Builds out of the box with no dependencies. Works in embedded devices and iOS.
Written with portability in mind. Builds in GCC and Clang.
MIT license. Link with open and proprietary software, no strings attached.