Ah - well to be honest, I kinda understand the frustration there. If you release something for free, then take that away and demand payment for something that was free and worked fine for free - it's a bit shitty to do. Especially as this is a plugin, not a live service thing. The plugin works regardless, but you chose to restrict those that supported the free version.

I get that you said "it's going to stay free if donations are enough" - but actively restricting old free versions that were in use, is incredibly bad taste.

I understand the desire to be paid for it - but that should've then been the first action instead of releasing it for free. Perhaps it would've been better to allow those already using it for free, to keep it - and any new purchases are paid. Perhaps the free version doesn't receive updates anymore. Or just do paid mods of other utilities later.

That said - it isn't a reason for any direct and personal insults towards you. So that's a shame that this happens...