Minerva (QDOS reimplementation)
Written by Laurence Reeves in England, Minerva was a reimplementation of Sinclair QDOS, the built-in operating system of the Sinclair QL line of personal computers. Minerva incorporated many bug fixes and enhancements to both QDOS and the SuperBASIC programming language. Later versions also provided the ability to multi-task several instances of the SuperBASIC interpreter, something not supported by QDOS.
Minerva was distributed as a ROM chip on a daughterboard which replaced the QL's original ROM chips. A Minerva Mk. II daughterboard was also produced which also incorporated an I²C interface and non-volatile real-time clock. As of version 1.89, the Minerva source code is licenced under the GNU General Public License.
Other reimplementations of QDOS include SMS2 and SMSQ/E.