The simpler media website CMS
Just to share a thing that might help someone else.
I had an issue rather like this one except attempting to run Setup resulted in 403 errors. The links to run Setup ended in .php and I had mod_rewrite enabled. I think that was the issue. mysite/zp-base/setup/index.php was there and permissions set to 644, but still it would 403 on me.
Editing the url link to mysite/zp-base/setup/ worked. Then once that had run, the link at the bottom threw another 403 error as it included index.php in the url. Deleting that worked - so it was something like setup/?more-text-here
It took me a few hours to figure out. I even tried upgrading to 1.5.1 in the process, but that stuck in the 403 thing too. Now I know to delete the index.php from the url I might try again in the morning.