EDIT: I forgot to write a bit more about the license issue

this video from Louis Rossmann is worth to watch to know more about the author and the Grayjay project and the license.

the video was banned from youtube, so here it is: https://odysee.com/@rossmanngroup:a/the-best-way-to-watch-online-video-my:c

The license is not Free and Open Source Software(FOSS) as we are used to. It is a custom view of open source. You can modify the code for your own personal use, but not redistribute it for commercial purposes. You cannot modify the part of the code that deals with the payments to Futo.

I think they are monetizing the software by selling the licenses while providing the full code to show that there is nothing bad in the app and they fear that with an FOSS license, someone would fork it and remove the payment and insert malware into it as it happened with NewPipe.

Here is a stamenet on the topic from Futo: https://web.archive.org/web/20240616233748/https://www.futo.org/about/futo-statement-on-opensource/

Video: more explanations about the license: https://www.youtube.com/watch?v=lCjy2CHP7zU

the important part of the license:

FUTO Holdings, Inc. (the “Licensor”) grants you a non-exclusive, royalty-free, worldwide, non-sublicensable, non-transferable license to use, copy, distribute, make available, and prepare derivative works of the software, in each case subject to the limitations below.

You may** use or modify the software only for non-commercial purposes** such as personal use for research, experiment, and testing for the benefit of public knowledge, personal study, private entertainment, hobby projects, amateur pursuits, or religious observance, all without any anticipated commercial application. You may distribute the software or provide it to others only if you do so free of charge for non-commercial purposes. Notwithstanding the above, you may not remove or obscure any functionality in the software related to payment to the Licensor in any copy you distribute to others. You may not alter, remove, or obscure any licensing, copyright, or other notices of the Licensor in the software. Any use of the Licensor’s trademarks is subject to applicable law.