Q-Liberator BASIC compiler is now available once more, from SellMyRetro.com thanks to an arrangement between RWAP Software and Jochen Merz. The most recent version is v3.36 and costs £33 from

See http://www.sellmyretro.com/offer/details/sinclair-ql-q-_liberator-superbasic-compiler-11891

The QLOAD/QREF utilities, also from Liberation Software, is also available from SellMyRetro.com. The QLOAD part creates faster loading tokenised SuperBASIC program files, while QREF is a programming aid for BASIC, allowing you to do things like searching for variable and procedure name in a BASIC program, list occurrences of variable and procedure names used and so on. QLOAD/QREF available for £15 from http://www.sellmyretro.com/offer/details/sinclair-ql-qload-~~-qref-superbasic-utilities-11892