Ok, so I've bought the game and downloaded the .sh file.
I've made it executable with read and write permissions.
But when I run it, it gets to the point when it asks you to accept the user agreement, and then freezes m entire laptop. The installer UI doesn't change, it still shows the agreement. When I eventually get it to close, the terminal says that it 'couldn't run mojosetup'. I've trawled around the Internet for a bit but couldn't find anything.
I've re-downloaded the file to make sure it wasn't corrupted or anything, but heres the md5sum thing anyway: 649c1bf9d7ccd81553c574ff1bec2cef.

@blairCross

My gog_planescape_torment_enhanced_edition_2.1.0.3.sh has the same md5sum, and it works fine for me.

No idea what's causing your issue, but be sure the check the standard stuff like:

* Do you have enough disk space?
* Does your laptop meet the minimum system requirements? (Try closing all other programs before running the installer, especially ones that eat a lot of RAM or write to disk a lot, e.g. Firefox or Chrome.)

If you can't get it to work, it's best to contact GOG support. (Be sure to state what Linux you're using, and what the laptop's specs are.)