Yes, the bundled plugins work. I have start.php in mod/<plugin_name>/start.php. I used -R on my chmod and my chown, with apache.apache ownership. The only difference I can imagine is that I used "chmod 775" instead of "777", but I'll check that next. I'm sure it's something stupid, like my first marriage. Thanks for the sanity check. I could have used it in 1982.

Since Elgg core doesn't need write permissions in htdocs only read rights (for the apache user/group) should be enough.

PS: never set permissions to 777, save should be 755 for folders and 644 for files.

Are you sure apache:apache is correct for owner and group?  You can try with (as root on the server)

apachectl -S

to find out the user and group the Apache process is configured to run as.

As @Jerome already said, 777 within the install folder / plugin folder is not a good idea. You can change folder permissions recursively with

find . -type d -print0 | xargs -0 chmod 755

and file permissons with

find . -type f -print0 | xargs -0 chmod 644

while inside the plugin folder you want to change the permissions of. Then don't forget a

chmod 755 <plugin_name>

while in the mod directory.