The publishers could require significant fees to be paid to them if their material is reproduced by someone else, but in the case of passing of rights from the original publisher who first own the copyright of a content and somehow the copyrighted content is a decade old then the later publisher will charge a high cost for republishing the content will be considered to be abusive to that right especially when the one who want to acquire the content will just take a phrase or some part of the content. Nevertheless, it is a crime to publish content without prior notice to the author or publisher of the content.
In addition to that it will not be ethical to make modifications of diagrams, figures, pictures, sentences, terminology and etc. Therefore, making changes to any copyrighted content just to avoid the payment of permission fees to publish it, is not ethical at all. But the publisher also should consider when making decision about permission fees, and also the publisher should not hinder the progress of certain knowledge in any other way.
For software, it depends if it is permissible to take another person’s code, and make limited modification to it. If it is open source code then it is permissible to do modification and present it as your own work provided by giving proper credit of the previous creator of the code. But if it is not an open source then it is not ethical, especially those software that was cracked by other programmer. And also before someone will modify open source software, it is a must to first read the term and condition concerning that software.
Finally, about what is ethical or not ethical, there are enough books that cover all the issues regarding some professional dilemmas. Whatever it is that benefit the majority then it is ethical but we know that it will not apply if the matter applies legal entities, the issue about legal spectrum will defer from another. So whatever it is make it sure that in every action that will be made, we know the legal parameters.