There is no code size limit on the compiler but it has an evaluation mode that it reverts to when it does not have an activated license. In this mode it will not build applications greater than 2kB.
When you install the compiler you have 30 days to activate the license. If you do not activate the (free) license then the compiler will revert to evaluation mode. Depending upon what you are doing when the license expires you will get an error from the compiler (INCORRECT LICENSE ID CODE (LIC) IN 'TOOLS.INI') or the linker (RESTRICTED VERSION WITH 0800H BYTE CODE SIZE LIMIT).
Note that the license can be renewed at any time and lasts for a calendar year. You may renew it, for free, as many times as you like.
For details on how to activate your license refer the Knowledge Base article PSoC Creator - Keil Compiler Registration