Install without composer?

I there any way to install all required libraries without using Composer?

You need composer because we rely on the autoloader it generates.

This issue is a duplicate of #2858750: Possible to download Solarium library manually?. It contains some more information.

What is the simplest way to install Composer to existing Drupal installation?

I already descibed one way here: https://www.drupal.org/node/2763951#comment-11392003

@ superfedya:

In terms of PCI compliance, its important to manage permissions, users and groups correctly.
A package manager used to keep track of software dependencies and work with them can be very helpful for devs. Production sites with an emphasis on security usually have site files that run under strict access permissions and these files would not really be writable to a user or a process that was not SU or a user associated with a webserver. Composer has it's place in the development environment but it should not be necessary to run it on a production server. In the context of PCI compliance, composer on a production server could be considered a vulnerability because it could grant power to a malicious user to access data or programs, and thereby compromise data security and integrity.

https://digitalguardian.com/blog/what-pci-compliance

I second @earlybug. composer should not run on a production server. It should "compose" your software on a staging or build environment. The result has to be deployed to production.

I started my site before I knew about composer and do not have it installed. I am reading that it is near impossible to start managing your Drupal 8 project with composer if you didn't create it with composer. I have Ludwig installed and it works great for other projects, but sadly not for search_api_solr. I need to install search_api_solr for a critical project. Is there any other way to install it (other than with composer) or is there an alternative module that is more user friendly?