> It is claimed Synergy 3 will arrive in 2022 or 2023, which I expect (no insider info) will likely be a lipstick-on-a-pig Electron UI around the same buggy core they've been prodding for 10 years without substantial enhancement.

They claim they are hiring Node.js and React developers to deliver something with "the rock-solid stability of C++".

So I'd wager you are correct with an Electron UI.

Was that tax bill why it went completely commercial around 2018 and why the company became headquartered in the Isle of Man? If so, how big of a tax bill was it and for what tax(es)?

In the UK company directors can borrow money from their companies, but if it isn't repaid after a certain duration a tax of 32.5% becomes due.

The public record[0] tells the story

      Year end April 2017:
        - Number of employees     : 6
        - Directors Loan          : £238K 
        - Balance sheet           : £154K
        - Tax due                 : £60K

      Year end April 2018:
        - Number of employees     : 8
        - Directors Loan          : £999K (prev rolled over)
        - Balance sheet           : £736K
        - Tax due                 : £303K

      Year end April 2019:
        - Number of employees     : 2
        - Directors Loan          : £1.27M (prev rolled over)
        - Balance sheet           : £1.1M
        - Tax due                 : £307K

      Year end May 2020:
        - Number of employees     : 1
        - Directors Loan          : £253K (£1.1M has been repaid)
        - Balance sheet           : £227K
        - Tax due                 : £15K

Repaying the loan would have allowed for the 32.5% tax owed by the company to be reclaimed, then regular corporation tax of 19% and personal dividend/income taxes would have been paid.

My theory is that his directors loans were fully invested in personal assets (or spent), which explains why the tax wasn't ultimately paid in 2018/19. So he nerfed the company so his tax bill could paid from revenue earned between mid 2018 and early 2020. This fits with the fact that he only started rehiring seriously in 2020.

Customers effectively paid for unmaintained open source software during this time. Now of course, on the website, he brags about how much he loves customers.

I can't speak for the IoM move specifically. I know the CEO has familial connections there, but I'm sure the confluence of tax advantages helps.

[0] https://find-and-update.company-information.service.gov.uk/c...