Linux4Chemistry classifies software into five categories, which are defined as follows:
This is software which is available at no cost, for which the source code is freely available, and which can be freely modified and distributed. More specifically, Linux4Chemistry defines as Open Source software which is either public domain, released under an OSI (Open Source Initiative) -approved license, or whose license appears to be compatible with an OSI-approved license.
This is software which is available at no cost to everyone, but which is not Open Source.
Free for academics
This is software which is available at no cost only to those using it for research purposes, at not-for-profit institutes, or for non-commercial purposes. You need to look carefully at the license for the software to see whether you will be charged for its use. Note: some software is available for free to academics only from a particular country. This has been classified as commercial software but a note is appended to the software description.
Software you have to pay for. Note: they may be available at no cost for a trial period.