What is Inno Setup?

Inno Setup version 5.6.1
Copyright © 1997-2018 Jordan Russell. All rights reserved.
Portions Copyright © 2000-2018 Martijn Laan. All rights reserved.
Inno Setup home page [external link]

Inno Setup is a free installer for Windows programs. First introduced in 1997, Inno Setup today rivals and even surpasses many commercial installers in feature set and stability.

Key features:

Is it really free of charge, even for commercial use?

Yes, it may be used completely free of charge, even when deploying commercial applications.

(Note: "Completely free of charge" must not be confused with "completely free". Inno Setup is copyrighted software, not public domain software. There are some restrictions on distribution and use; see the LICENSE.TXT file for details.)