The 'new' bootloader for MPIDE/chipKIT PIC32 boards
This bootloader is buildable for all currently available official chipKIT boards (UNO32, MAX32, uC32) as well as many "3rd-party" boards (meaning other boards that either happen to work with MPIDE or were designed that way, but not by Digilent) like the UBW32 and Fubarino boards.
The bootloader codebase supports two methods of bootloading - over UART (async serial) or USB CDC-ACM (virtual serial). These two methods are mutually exclusive in the current bootloader code - for a given board, you build the bootloader for EITHER serial OR USB, but not both. This decision is made by which files are included in the build, and the #define CAPABILITIES in the BoardConfig.h file. Note that many boards (like the chipKIT Pi and UNO32) have two bootloaders, one for UART and one for USB.
There is a single project and multiple build targets for MPLAB X. To build the code requires MPLAB X and the XC32 v1.31 (or higher) compiler. Note that the full size optimizations are needed for this bootloader, so the free XC32 won't work for all of the bootloaders (although it may work for some).
IMPORTANT NOTE: While the majority of this code was written and tested by Keith Vogel of Digilent Inc., this software is NOT a product of Digilent Inc. and Digilent will provide no support for it. They have gracefully contributed this code as open source code to the MPIDE community, and it is now being maintained and supported purely through the ChipKIT forums (http://www.chipkit.org/forum/index.php) and the GetHub repo site (https://github.com/organizations/chipKIT32) for code updates and issue tracking. This means that the official bootloader HEX file for a board purchased from Digilent is NOT contained here. If you want the official HEX file for the bootloader for your Digilent board, you should go to Digilent's website and download it from there. You can of course also use the bootloader HEX files from this codebase, but they are not official Digilent bootloaders.
The BoardConfig.h file contains all of the board-specific information (what capabilities the board has, what pins the LEDs and buttons (if any) are on, what the config bits are, etc.).
This GitHub repo also contains 'update-sketches' which are proof-of-concept MPIDE sketches that can be used to over-write a bootloader with a newer bootloader. They are provided by Keith Vogel of Digilent without any support. But they can be terribly useful.
The BootloadersCurrent-hex folder now has the very latest hex files for all supported boards.
To use one of these hex files, you'll either need to use the update-sketches or an ICSP hardware programmer like the PICKit3 from Microchip.