There SDCC http://sdcc.sourceforge.net/ , and the Microchip compiler itself is also free for student / hobby projects.
I have never used SDCC, and it seems to be a little rude from what I read.
The Microchip C compiler works fine and is more compliant with the C standard than CCS.
But I prefer the CCS wrapper around the API. And it’s not expensive.
, - , CCS, .