I consider 0.3/0.4 the same version, there wasn't any official 0.4 release, we were just calling trunk in the private subversion 0.4 to distinguish it from the 0.3 releases. Whatever floats your boat. To address your concerns:
- Cast system isn't added because no one has contributed a good enough system yet, there is one in the works as an open pull request at the moment. You can apply it to your codebase if you are eager to have a cast system.
- mayNotMove wasn't only removed because of the function name, but also because of the way it was implemented. I think I've written about it on GitHub and I don't feel like repeating the reasons. To put it short: it wasn't bulletproof, it was added in a hackish way. mayNotLogout has similar reasons, but can be achieved through no-logout tiles or the onLogout creature event. mayNotMove will be possible to use by different means in 1.1, until then you can use onStepIn and teleport back.
- The lack of item attributes is for memory and performance reasons, but will be reconsidered in 1.1.
- Compat is only designed to cover 0.2, if you are switching from 0.3, it's not my concern as I was never supporting it.
- You can still do the same things without mods, it's more like a bunch of related scripts packed into one XML file. Despite what others may think about it, I don't think mods are bad. It's much easier to manage (e.g. find the script you're looking for or disable a feature) related scripts with them, and they might make it into the 1.x series at some point. It just hasn't been a priority.
- Animated text has nothing to do with the server, it was removed at some point in a client and if that's your only argument for 8.6 you're not seeing the big picture (mounts, market, new graphics, inbox, etc.).
Item attributes, by using: item:setAttribute and item:getAttribute. See the script reference on GitHub.
Combat options isn't as customizable as we want it to be yet, but I think the default is retro-style.
Sprites are on the client side, so whatever you did with any other TFS version should apply here too.
The reason why you're having a hard time compiling 1.0 is because you're being stubborn. Dev-Cpp is ancient software, it seems to fit your idea of using 8.6 and 0.3 so it's probably the appropriate choice for you, but here's some news from 2014: Dev-Cpp hasn't been updated for 10 years. Dev-Cpp is insanely slow. It's Windows only. It isn't a compiler, it's an IDE that is packaged with MinGW (like Code::Blocks), and you can compile TFS 1.0 using MinGW too, just use CMake and it will take care of most stuff for you.
Installing OpenGL to be able to compile any version of TFS is the most ridiculous thing I've heard today.
Anyone is welcome to make major changes, just submit a pull request which complies with our code guidelines and it will be reviewed and merged if it's good enough. Fallen hasn't even made any major change so I don't even know why you brought up his name, nor does he have access to commit to the repository. To put it short: know what you are doing if you want to contribute, because we try to maintain high quality code and don't want to deal with copy & paste code that you want to force into the project just because it suits your needs, compiles and works for you. Understand why it works and if it is the most optimal solution for everyone. If you don't like that, you are welcome to maintain your own fork.