RNAstructure 6.4 could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The actual developer of the free software is David H. Mathews. The program is categorized as Education Tools.
We recommend checking the downloaded files with any free antivirus. The latest version of the software can be installed on PCs running Windows XP/7/8/10/11, both 32 and 64-bit. The program's installer files are generally known as RNAstructure.exe, _294823.exe or _bb32ea6.exe etc. The following versions: 6.1, 5.7 and 5.6 are the most frequently downloaded ones by the program users.
From the developer:
RNAstructure is a program for RNA and DNA secondary structure prediction and analysis. It can also be used to predict bimolecular structures and can predict the equilibrium binding affinity of an oligonucleotide to a structured RNA target; this is useful for siRNA design.
You may want to check out more software, such as PolicyMaker, CAP 540 or GASEQ, which might be similar to RNAstructure.