If you're on windows, all you have to do to run from source is:
Download this file:
https://github.com/kovidgoyal/calibr...ads/master.zip
extract it to:
c:\users\your-windows-username\
(example path)
then run this bat script:
set "CALIBRE_DEVELOP_FROM=C:\users\your-windows-username\calibre-master\src"
start calibre
(just save that in a txt file and give it a .bat or .cmd extension)