On Sun, 14 Mar 2021, angel2000(a)onet.com.pl wrote:
 Hello,   I'm a student and I need to download the gretl but when
I 
 try to install it the "error" comes out. It says that the current 
 version of gretl is not updated for my version of iOS (I have 
 MacOS Big Sur version 11.2.3). I have no idea what should I do but 
 it says I need to contact the developer of the application and the 
 developer have to update this one.
 I added attachment with what I see when I want to download the 
 gretl.  
What do you see if you click the "More information" button?
And have you looked at the instructions (for Catalina, but may work 
for Big Sur) at 
http://gretl.sourceforge.net/osx.html ?
Allin Cottrell