-Rars are used for convenience, as they have some features that the old archives lack. For example when making a test build of the game, it's faster for us to update the archives than to repack them from scratch when making small changes for testers.
-Watermarking the installers with username is not planned. One, for ideological reasons, two it's not really technologically feasible.
-Yes, the archives are password-protected. Here's why:
The supported way of installing the games is by using the Installer, which apart from unpacking the files, also creates registry entries, shortcuts, compatibility fixes etc. We want to avoid having the situation, when user will see a unprotected rar file, download and unpack it, and get a "broken" installation, because he didn't use the installer.
There were situations, when users would download just a single part of the installer, or try to unrar it manually (because apparently some browsers detect our new archives as rar files), or even try to open the .bin files with the VLC Video Player.
In such a situation I think it's better to give immediate "it won't work that way" message, rather than allow someone to make a "partial" installation, which may or may not work, without any information.
Another reason - I want to avoid the situation where someone tampers with the archives (let's say adding malware, or some illegal content), and uploads the modified version on torrents. I don't want the GOG Installer installing anything else than it was supposed to, and it doesn't matter how it was obtained.
The Installer is designed mostly for reliability and ease of use for any user. And it's intentionally designed as it is.
Mind you - if you are using the supported installation mode, you don't have to enter the password anywhere. Nor is it in any way dependent on username, or hardware, or anything else. It's more or less hardcoded into the installer (I see you guys already figured out how), as much as the decompression algorithm. You can still use the installer exactly as you could since the beginning of GOG, and install your games wherever, whenever, and however many times you want. It doesn't detect where was it downloaded from either. That hasn't changed at all.
We don't really support installing the game by manually unpacking the archives (for whatever reason you do that). On the other hand, I see you already figured out the algorithm for obtaining the password, so you are still able to do as much. I'm not going to say "Hey, good job hacking into our software guys!", but I'm not going to try and make the password harder either.
want to use the GOG installer. It's the best thing ever. Leaving little impact on the registry and somehow knowing what the game save files are. Not sure if this happens on the Linux version but still. I really like the GOG installer. I with more companies used it.