In about 1991, Software Components Group was acquired by Integrated Systems Inc. (ISI) who further developed pSOS - now restyled pSOS+ - for other microprocessor families, by rewriting the greater part of it in C. Attention was also paid to supporting successively more integrated development environments, culminating in SNiFF+.
In 1999 Integrated Systems Inc. 'merged with' (in reality they were taken over by) Wind River Systems, the originators of rival RTOS VxWorks. Despite initial reports that pSOS support would continue, development has been halted. Due in the near future is a 'convergence' version of VxWorks which will support pSOS system calls, and it has been announced that no further releases of pSOS itself will be made.