Someone told me that since the compiler/loader is open source, it may create erroneous code or may create code that conflicts with boot or loader code, and that this was a reason one shouldn't use the Arduino for commercial apps.
Nonsense. Open source software is used FREQUENTLY in commercial products, and not just for compilation. Most of the internet is built from from such products (cisco router software is compiled with gcc, and has been for over 20 years (though multiple generations of multiple architectures of CPUs), and many of the home routers are actually tiny linux boxes.) And NOT being open source hardly guarantees that software (even compilers) will be bug-free (look at windows 
(or those cisco routers' bugs, very few of which can be blamed on compiler incorrectness. Sigh.)
While arduino hardware is not "hardened" against "industrial environments", it isn't any less so than many other commercial products; we've bought "temperature loggers" that weren't much more than a PIC and an rs232 interface. Being able to cover a temperature range from below freezing to "overheating" might require special attention, but that'd basically be attention beyond that needed just for "commercialization."