DynaFit 4.04.061 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The software lies within Education Tools, more precisely Science Tools. This free program was originally created by BioKin. We recommend checking the downloaded files with any free antivirus.
From the developer:
The main purpose of the program DynaFit is to perform nonlinear least-squares regression of chemical kinetic, enzyme kinetic, or ligand-receptor binding data. The experimental data can be either initial reaction velocities in dependence on the concentration of varied species (e.g., inhibitor concentration vs. velocity), or the reaction progress curves (e.g., time vs. absorbance).
You may want to check out more software, such as Panel, SatCalc or MemBrain, which might be related to DynaFit.