Free in this case means that the monetary cost for the learner is zero. There are some resources that ask for donations, and there are some resources that provide some of the material or learning opportunities for free and for the rest they charge. On this website, I only list resources that are fully free. In other words, any learner who pays and who does not pay have access to the same materials and opportunities.
The resource has to be free as further defined above. It should not be time sensitive, as in, there is this workshop that will take place on Thursday. The main reason is that I do not have the time to update the website often so resources that are (sort of) permanent are preferred. There are some amazing package documentations out there as vignettes. However, they will not be listed here mainly because there are many of them.

If the resource meets these criteria then please submit the resource by filling out this form.
There may be many reasons. I might be busy with work and may not have the time to update the website. The resource may not be fully free (see definition above). It may not be suitable for one reason or the other. I will try my best to communicate with you.