Davis Thanks for this reply Davis, that explains a lot. I just contacted the host and they won't even tell me how much memory is allocated (for security reasons) but I can't really tell what's taking up all the resources. I'm running Composer from the place it's globally installed:
php ~/.php/composer/composer require santiagobiali/flarum-ext-logo
and no matter what the process is killed.
Is there another way to change the header logo by hand instead of using this extension?