Latest firmware is available at the main page of the device. In the wiki one can only find older firmware, that still might be helpful. The projects listed below are no longer officially supported. The best practice is to use the EXACT same compiler as mentioned and in most cases the exact same MPLAB version as mentioned.
Older firmware released by Olimex for MOD-TC-MK2-31855:
1)MOD-TC-MK2 firmware v2 source (for MPLAB X and HI-TECH C 9.83) and explanation - https://www.olimex.com/Products/Modules/Sensors/MOD-TC-MK2-31855/resources/MOD-TC-MK2_firmware_OLinuXino_v2.zip
2)MOD-TC-MK2 firmware v2 in binary format - https://www.olimex.com/Products/Modules/Sensors/MOD-TC-MK2-31855/resources/MOD-TC-MK2-v2.hex