By using this chip and a blank MKL26Z64VFT4 or MK20DX256VLH7, you can build your own Do-It-Yourself board that's compatible with Teensyduino and Teensy Loader. Either chip will work. The MINI54 will automatically detech which chip you've used and implement either Teensy LC or Teensy 3.2.
These chips can also be very useful for modest volume production of a fully custom product developed using Teensy LC or Teensy 3.2.
The MKL04 and MKL02 chips are functionally identical. The only difference is size. MKL02 is a tiny 3x3 mm QFN with 0.5 mm pitch pins, useful for designing the smallest possible board. MKL04 is a larger 7x7 mm TQFP part with 0.8 mm pitch pins, useful for prototyping with manual or hot plate soldering.