You can get the latest git archive here.
Inside the ZIP you will find two folders:

• Streamlink for Windows (Compiled): The program executable, intended for end users.
• Streamlink for Windows (Source code): The program source code, intended for developers.

A program to build a portable version of Streamlink for Windows.

Windows 7 SP1 or later with .NET Framework 4.5 or later.

Build between three flavors:

• Portable EXE (Recommended): For users who prefer to have all available files in the same folder.
• Standalone EXE: For users who prefer to have all files packed within the executable.
• Portable BAT: Same as Portable EXE but a batch file is generated instead of an executable.

By default the building source is the latest available commit (nightly) or the latest stable.
No system files are modified and you can run it from anywhere (such as flash drive or other external drives).

Yes, you can find precompiled releases here.
Note that only stable releases are available, for nightly builds you have to use the program.

Feel free to open a new issue here.

Feel free to open a pull request here.