The quote at the end of the posted Reuters article (not the one you’re responding to) says that it doesn’t require extensive code modifications. So is the “custom software” is standard for the target customers of nextsilicon?
By the time special chips were completed and mature, the developers of "mainstream" CPUs had typically caught up speedwise in the past, which is why we do not see any "transputers" (e.g. Inmos T800), LISP machines (Symbolics XL1200, TI Explorer II), or other odd architectures like the Connection Machine CM-2 around anymore.
For example, when Richard Feynman was hired to work on the Connection Machine, he had to write a parallel version of BASIC first before he could write any programs for the computer they were selling: https://longnow.org/ideas/richard-feynman-and-the-connection...
This may also explain failures like Bristol-based CPU startup Graphcore, which was acquired by Softbank, but for less money than the investors had put in: https://sifted.eu/articles/graphcore-cofounder-exits-company...
Modifications are likely on the level of: Does this clang support my required c++ version? Actual work is only required when you want to bring something else, like Rust (AFAIK not supported).
However, to analyze the efficiency of the code and how it is interpreted by the card you need their special toolchain. Debugging also becomes less convenient.
If they provide a compiler port and update things like BLAS to support their hardware then higher level applications should not require much/any code modification.