Yes, the browser executable is a trial version while the full package is the paid one. At least for now.
It could be confusing due to having first the language selection screen but once in the title screen it is stated that this is the demo.
To add to the matter, while technically it is already a full game, to my taste it's not already finished. Due to this I plan at least to release a 1.1 in the very near future.
Also, the fact that there is almost no sound is not a bug, but part of the style I was looking for. Like in the 80s when the OST came in a different tape to hear while playing.