Tcllib and New License Addition?

Hello,
I came across the license_fsul.terms file in the Tcllib repository. The license conditions seem interesting and unconventional, as they require payment for productive use. To me, this is rather unusual for an open-source library, so I wonder if this was indeed intended or if the file was perhaps added by mistake.
https://core.tcl-lang.org/tcllib/file?name=license_fsul.terms
best regards
Gregor