I can certainly sense your frustration.
You don't have to pay anything if you don't want to.
I too use SA and love it. It also cost money, and I am happy with the performance I got for the investment.
I am sorry I don't know any of the history behind this development or who syssi is or what they did, all I know is this finished useful product came about from some amount of work/effort and to me it appears to be a great step forward, unavailable without uksa007's contribution.
If he has or owes anyone else for a portion of the development I would expect that is between them to sort out.
This is what patent law and copywrite is all about; ask Robert Kearns, Rosalind Franklin, and Nikola Tesla.
First, I'd like to echo the same gratitude in regards to uksa007's original contribution(/improvement) as an open source solution. Open source is NOT at all about money, patents, or copyright. It's about contributing to an idea, bringing it to the next level, and sharing how it was done with the community. The next person does the same. Switching to a closed codebase is against the entire open source philosophy, and prevents community improvement as a whole.
Let's look at the statement, "...unavailable without uksa007's contribution". If syssi never released esphome-jk-bms (which by the way, handles the majority of jkbms comms and esphome integration), this fork likely would have never seen the light of day. While we're giving credit to uksa007, bear in mind it is entirely based on syssi's original contributions and framework (which relies on esphome, etc etc...). Go ahead, compare the git repos. If we're giving credit, let's give credit where credit is due.
As for my personal experience - I was about halfway done with my own JKBMS to CAN implementation before stumbling upon this, which did about 95% of what I needed. No need to re-invent the wheel. Is it perfect? Not by a long shot, but it gets the job done. However, due to the open source nature, I was able to fix a few bugs and add custom functionality I needed for my own setup. Now, in a closed environment, this will no longer be a consideration, I will seek other options moving forward.
As an open source supporter, I am quite disappointed with the direction of the project. However, I respect uksa007's decision, for whatever reason that may be, and am thankful this was provided openly at all. Supporting an open source project takes a lot of work, and at some point, it's a personal decision to figure out how to pay the bills.