OpenBSD is somewhat controversial in that a variety of its security claims don't make sense or work out in practice. As a whole, however, they do meaningful work so it's still worth donating.
What do you exactly mean by "its security claims don't make sense or work out in practice"?
I use OpenBSD as a daily driver. To make GP's point though, there are a few video's [0] and blog posts dissing OpenBSDs security claims.