> I know nothing about J and JSoftware, but this reads like an Aprils fools joke. Is it?

To me it reads as being colored by a very specific tool bias. For example:

>> The key difference between Jd and most other database systems is that Jd comes with a fully integrated and mature programming language.

Most major database systems come with a fully integrated and mature programming language.

>> Row orientation works for small amounts of data.

It works for a different data access pattern. Row vs column is a tradeoff spectrum. Data size is just one dimension of the analysis.

>> Row oriented is slavishly tied to the design ideas of filing cabinets and manila folders. Column oriented embraces computers.

Pretty hyperbolic.