The final shareware version (2.6) was fairly comparable to the retail version (2.7). This says the shareware version just lacked some sound effects...? https://web.archive.org/web/20091129230733/http://wiki.gible...

However, I believe the first shareware version I had was 1.x (distributed via CD that was packed full of shareware) which was significantly different. I remember mining fuel, which tracks with the above link.

Stars! was one of my very first video game purchases. I remember mailing a money order, and recieving a copy in the mail - I didn't have internet at the time. I'm not sure I even knew the internet existed then, although I would soon after if not.

AFAIK this was the case. I played a lot of Stars! (almost exclusively the shareware) and it had all the races and tech trees. It showed higher level tech trees but those were only available in the registered game. Map sizes were also limited in the shareware. Later versions might have required additional resources for the retail upgrade but I believe the version I had (2.5?) could become the full registered copy with just a key.

The shareware version I had was missing stuff until I upgraded. It was before 2.0 came out, but I don't remember the details after all this time. I believe it didn't have all the techs? Something important wasn't available.