Sinclair BASIC is a popular version of the BASIC (Beginner's All purpose Symbolic Instruction Code) programming language. Originally written for the ZX80, it is now available for a wide range of computers in native versions or via emulation.
Sinclair BASIC is copyright © 1980-81 Nine Tiles Networks Ltd, © 1982-87 Amstrad PLC, © 1983 Sinclair Research Ltd, © 1983 Timex Corporation.
The copyright is horribly complicated because Sinclair never owned the rights to Sinclair BASIC. All rights remained with Nine Tiles until Amstrad bought the ZX Spectrum rights. After the sale, the ZX80 and ZX81 rights stayed with Nine Tiles, the Interface I rights stayed with Sinclair and the TS2000 BASIC rights stayed with Timex. The upshot of which is that the Spansih version of the Spectrum 128 ROMs is technically owned, in part, by all of the above companies.
Nine Tiles Networks permits distribution under the GNU GPL. Sinclair has not stated its position, but has not sought to prevent distribution. Timex permits distribution. Amstrad permits distribution in software only providing it is accompanied by an equivalent of the following statement:
"Amstrad has kindly given its permission for the redistribution of its copyrighted material but retains that copyright"