KevinTheJedi Hurm. I got the same error, so I rinsed and repeated the whole process. Extracted the .phar, edited the .php file (making sure to overwrite the correct location), then copied it to the server. Changed the db install_path and isphar settings, and got the HTTP 500 error again.
I'm running v1.18.1 with OAuth2 Client v0.6
Any more ideas? If an updated plugin will be released within a week or two, we can probably wait it out, but it'd be great if we can get this working