where are the object files?

Sorry if this question sounds stupid, in the arduino.cc faq page, it says

Using the Arduino core and libraries for the firmware of a commercial product does not require you to release the source code for the firmware. The LGPL does, however, require you to make available object files that allow for the relinking of the firmware against updated versions of the Arduino core and libraries. Any modifications to the core and libraries must be released under the LGPL.

How do you make the object files/where are the object files located using the Arduino IDE?

Turn on verbose compilation in preferences. Do a compile. You will find where the .hex and .elf files are put (in some temporary directory usually).

Nick, thank you so much. Found it!

Turning on verbose is an eye opener for me. Should I be concerned with these "warning" messages?

warning: deprecated conversion from string constant to 'char*'

Some of the libraries generate warnings, in particular to do with progmem. I think most people ignore them.

Personally I would like the get rid of the known warnings and see the others (the real ones), but not just yet, it seems.