in ../diskw/docs/LICENSE.txt says:
----------------------
Uniform Server License
----------------------
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution. So I think that is Open Source software and you are able to make changes.