Like all applications, you need to give run-rights for a group you are a member off, usually the all-users group “Default”: Admin >> right click on the group >> Access rights >> Select run rights >> click on [+] and add home app
With a developer install you are responsible for installing all dependencies, in this case “phpgwapi”:
cd /path/to/egroupware
git clone git@github.com/EGroupware/phpgwapi.git
Ralf