v5.15 is easier to assemble, more robust, and (I hope) better documented. The zip file contains documentation in DocuBricks format, along with the STL files you need. The source code link provided by GitHub contains the original SCAD files and more STLs generated during development - please make sure to read the documentation before printing, and don't just print the contents of the STL folder. You need multiple copies of some parts and other parts are optional.
openflexure_microscope_5.15.1-rc0.zip