[sfpotter]

It does not show an unwarranted sense of self-importance on the part of Tim Davis.

Whether or not his style his widely known, his code is VERY widely used. Just look up SuiteSparse and try to find all of the downstream uses of it. It is one of the most---if not the most---ubiquitously used set of sparse linear algebra libraries. If you do anything with numerical linear algebra, there's a good chance you at least know what SuiteSparse is, and possibly also know who Tim Davis is.

The bigger issue here is the effect this has on research. Tim Davis not only programmed this library, he did the basic research leading to many of the algorithms in SuiteSparse. He went ahead and released SuiteSparse open source, probably thinking that it would be a good deal for him, provided that its use was properly attributed. Provide a public service in exchange for attribution. This is a reasonable way to get support as an academic. Clearly he has had a large number of industrial collaborations which likely have provided him with a significant amount of funding over the years.

Speaking for myself, if Microsoft has no compunction against behaving this way, I can no longer see the point in publicly releasing research code that I develop using an open source model. Microsoft is clearly telegraphing that they don't give a f** about licensing, although whether that holds if they are litigated against remains to be seen. I think there's an excellent chance many other researchers feel the same way. If you think openness and reproducibility in science is important, this is a problem.