The source code of the LokiCheckout is partially open source (OSL v3.0), partially released under a custom license. In general all open source packages are released via GitHub. All shared source packages are released via GitLab.
If you are still using the Luma Checkout, your webshop are probably missing out on more revenue: Page loads are horrible, especially under mobile devices. The JavaScript stack of Luma is heavily outdated (KnockoutJS, RequireJS, jQuery, jQuery UI) and oversized - it is not uncommon to load 2Mb of JavaScript. And especially within the checkout, this hurts conversion. The LokiCheckout drastically improves this.
Plus the code is much cleaner and easier to extend.
Things can always be improved. As a developer, agency or merchant, we believe you almost have the obligation to investigate alternatives if they come to rise. Not investigating options might mean that you are missing out. So here it is: LokiCheckout improves things even more, compared to the Hyvä Checkout. And we're happy to proof this to you.
What is faster with the LokiCheckout? There is no other JavaScript library than Alpine (~50Kb). Hyvä Checkout adds an additional 160Kb because of Magewire. Next, with Magewire, component updates are done asynchronously, due to which component update needs to wait for another component update to be completed. With Loki, there is only 1 single AJAX call to update everything. Bam.
What is more flexible with the LokiCheckout? There is no complex form API to extend your address forms, just use the XML layout. Code is even more straight-forward and easier to adjust. Additionally, we actively apply testing for numerous things. Once you dive into it, you will experience this yourself.
Unfortunately, there is no demo of the Magento Admin Panel available. However, we have developed a mechanism that automatically includes the configuration options in our online documentation on this site. Every module always has a developer docs in which that configuration can be found. And more and more modules also have a less technical user doc with screenshots. That way you hopefully get a good impression.
Note also that, with the LokiCheckout, the available configuration options are less important - they don't show the actual benefit of the LokiCheckout. For example, if you want to know what a combination of a certain PSP and the LokiCheckout does, there is no backend setting that can be toggled. It is about installing composer packages, enabling the modules and seeing things in action on the frontend.