For the first issue, it's a strange problem, but are you typing forum.app or forum.app/? The former will trigger a Google search. The latter will trigger accessing your local development site.
For the second issue, what's your bootstrap/start.php look like? It should be hardcoded to look for 'homestead' as the hostname and then set the environment to development. If that happens, then you should get the typical error page.
I am typing forum.app not the slash, and also, my start.php has 'local' => array('homestead'), hardcoded. Also, might be something wrong with my Yosemite's DNS because even a PHP Built-in web server won't work unless I explicitly do php artisan serve --host 127.0.0.1. The localhost always seems to say Can't get address etc. This problem is madness.
Okay, so is there anything wrong with me making this work on 127.0.0.1:8000 ? By the way, it somehow is accessible on 0.0.0.0:8000 too. Just asking. Meanwhile, I agree with the hosts bit, too many things to test. I'll just blame Yosemite :)
Hmm.. I too just rebuild my Macbook Pro with Yosemite and using the latest build for homestead. Your homestead.yml looks fine. The my host file looks like this
Another thing to consider, especially if you just did a fresh install of your mac, and you don't yet have to move anything around is do it again. I've had a bad install. And re-installing just made everything work. It happens. I've also had one bad install of homestead 2.0.
Lastly, I've used a fair amount of mamp and it does make some configuration changes, it's actually what drove me to homestead in the first place. If you do a fresh install, before you do anything else get homestead and vagrant, try and install it and the drop box for your files.
Once you have homestead running and your etc/hosts is set try it again, see what happens.