Why is Fork not installable into subfolders?
We think developers should try to keep the differences between the server and local machine as little as possible.
If you are developing with an url like http://localhost/projectname/ all your references will be relative, which is a hell when something changes. If you use an url like http://projectname.dev (can be done using virtual host setup on your local web server) you don't have to think about all those references, so you can use / as a starting point.
I got redirected to /install but don't see the installation wizard
The reason why you don't see the installer is because the url rewriting isn't working properly. Check if the .htaccess file is uploaded. Some operating systems or ftp clients hide this file by default.
If all files are uploaded, check if mod_rewrite is installed on your webserver and make sure your webserver accepts .htaccess files.
Still not working? Check the webservers article for a full read about working with webservers.