I use the Bootloader V5 from
Http://www.sprut.de/electronic/soft/usboot/usboot.htm (German Page)
Https://goo.gl/Z53QYX (Translated Page)
This starts after the reset when RE3 is at GND, or when the EEPROM cell with the address 0xFE has the value 0xFF.
Drivers / Tools for Windows are included in the USBoot package (Not Tested),
For Linux I use a customized version of fsUSB (http://www.internetking.org/fsusb/), or Piklab.
The device has its own USB ID:
Bus 004 Device 002: ID 04d8: ff0b Microchip Technology, Inc.