It is.
There are two types of PICs:
One-TIme Programmable - you can only program them once. No more programming or erasing. That's it.
Reprogrammable - can program and erase multiple times
WIthin these two categories, there are also software protected PICs. This means you can't read or modify their code (unless you had the source code to begin with. BUt you can completely wipe out their existing code and upload your own (or the original code that you modified, but you would need it's source from somewhere else- you could not read it from the PIC).
Reading the code from the PIC is kinda useless anyways...it'd be a bunch of assembly, not nice neat commented code or any high level languages like C.