The software world has changed over the last decade. Things move faster these days, so there are more (smaller) updates rather than occasional 'big bang' releases. Another trend is free operating system releases. Winner in this category is Apple, who's yearly OS X updates appear to break something badly every other year. Charging for updates isn't a natural fit in this landscape.
The paid upgrade revenue was rather substantial. To compensate for this loss there's now a Donate button, which you can use whenever you feel like saying 'thank you for the awesome update'. You can donate any amount, any time!
![Wink ;-)](./images/smilies/icon_wink.gif)
(*) Emails with upgrade instructions will be sent on October 30, 2015.
Giel Bremmers