EPPlus has from this new major version changed license from LGPL to Polyform Noncommercial 1.0.0.

With the new license EPPlus is still free to use in some cases, but will require a commercial license to be used in a commercial business.

This is explained in more detail here.

Commercial licenses, which includes support, can be purchased at https://www.epplussoftware.com/.

With the license change EPPlus has a new parameter that needs to be configured. If the LicenseContext is not set, EPPlus will throw a LicenseException (only in debug mode).

This is a simple configuration that can be set in a few alternative ways:

// If you are a commercial business and have
// purchased commercial licenses use the static property
// LicenseContext of the ExcelPackage class :
ExcelPackage.LicenseContext = LicenseContext.Commercial;

// If you use EPPlus in a noncommercial context
// according to the Polyform Noncommercial license:
ExcelPackage.LicenseContext = LicenseContext.NonCommercial;

using(var package = new ExcelPackage(new FileInfo("MyWorkbook.xlsx")))
{

}

  {
    "EPPlus": {
      "ExcelPackage": {
          "LicenseContext": "Commercial"
          }
      }
  }

<appSettings>
    <!--The license context used-->
    <add key="EPPlus:ExcelPackage.LicenseContext" value="NonCommercial" />
</appSettings>

This might be the easiest way of configuring this. Just as above, set the variable to Commercial or NonCommercial depending on your usage.

Important! The environment variable should be set at the user level.

EPPlus 5 comes with a set of new features, see https://www.epplussoftware.com/Developers/Features

• The default behavior for the Worksheet collection base in .NET Framework has changed from 1 to 0. This is the same default behavior as in .NET core today.
• Pictures have changed the behavior as the oneCellAnchor tag is used instead of the twoCellAnchor tag with the editAs="oneCell".
• ...and more, see https://epplussoftware.com/docs/5.2/articles/breakingchanges.html

EPPlus 5 has new, separate sample projects for .NET Core and .NET Framework respectively. There is also an updated developer wiki. The work with improving the documentation will continue, feedback is highly appreciated!

The latest builds from the EPPlus develop branch can be fetched from this Nuget feed