> Microchip provides free versions of their compilers. The only difference *I
> think* is that the paid version is "optimized" or something. I use the free
> versions of the C18 and C30 compilers and they work just fine with MPLAB.
>   
Free as in beer yes but not FOSS and that is IMO a problem for building 
something ardunio like arround it for a few reasons.

Firstly while C18 is kinda C it is somewhat quirky. For example it does 
not have sensible handling of the >> operator for negative numbers 
(there are workarrounds for this but they require great care), it lacks 
a unified pointer type meaning a lot of routines end up with two copies 
and so on. If it was FOSS someone could make a fixed fork but as it is 
we are stuck with it.

Secondly it may well forbid distributing your soloution as a whole (not 
sure on this, the license agreement for C18 student edition doesn't seem 
to be easilly availible online)

Thirdly it means linux distrbutions are unlikely to accept you or will 
shunt you off into a "non-free" area that is likely to be disabled by 
default.

Finally it means you won't get the support of the FOSS crowd.
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