"Quoatation [sic] from keil c51"

Well, if you're going to be pedantic, it's actually a quote from the document which describes the limitaions of the free Evaluation Version of Keil's C51.

"IMO, it's a compiler"

Nope.
It's a complete set of tools ("toolchain") - Compiler, Assembler, Linker/Locator, and IDE.

IIRC, the 2K limit applies to each part of the chain; ie,
* The compiler will not generate >2K of object;
* The assembler will not generate >2K of object;
* The linker will not generate >2K of output.