Keyoti.RapidSpell.dll contains the main controls for .NET 1.x use. This DLL can be used with .NET 2+ if desired, however it does not contain .NET 2+ features such as ContextMenuStrip or DataGridView.
Keyoti.RapidSpell.NET2.dll contains the main controls for CLR2 (.NET2 and .NET3) use. References to Keyoti.RapidSpell.DLL in this document and Keyoti KB articles can generally be interchanged with Keyoti.RapidSpell.NET2.DLL.
Keyoti.RapidSpell.NET4.dll contains the main controls for CLR4 (.NET4) use. References to Keyoti.RapidSpell.DLL in this document and Keyoti KB articles can generally be interchanged with Keyoti.RapidSpell.NET4.DLL.