Ada tasking is a powerful abstraction mechanism for developing concurrent embedded systems. However, many implementations of concurrent tasking have been seen as potentially unsafe for critical systems because of their high degree of indeterminism. The Ravenscar profile is a subset of Ada 95 tasking with purpose of providing a basis for the implementation of certifiable critical systems. ORK is an open-source real-time kernel which provides full conformance with the Ravenscar profile on embedded computers. The kernel has a reduced size and complexity, and has been carefully designed to allow the building of reliable software for embedded applications. This kernel is integrated in a cross-compilation system based on GNAT 3.13, supporting the subset of Ada 95 tasking which is allowed by the Ravenscar profile in an efficient and compact way. It is closely integrated with other tools, including a tasking-aware version of GDB.