Thanks to people in the Diocese of Salisbury for mentioning this source of news, Nyamilepedia, which I had never seen before. The story "Heavy Fighting in Greater Mundri" offers extensive detail on the SPLA attacks in Moruland.
The story's explanation of reasons for the SPLA's attacks are as follows:
"It’s not yet clear why the government of republic of South Sudan which has the responsibility to protect lives of the citizens and their properties stand with out any shame to fight the people of Greater Mundri in particular among other tribes of Equatoria Region.
"But much of the reasons to fight the people of Greater Mundri is assumed to be associated with the history of victorious fight the farmers had against dinka cattle keepers in between the year 2005 – 2006.
"As many people will be aware, since that fighting ended, there was no peace and reconciliation and healing done between the local community and the cattle keepers who are mainly the relatives of the government officials who send their cattle and relatives to grace and settle forcefully in the ancestral land which is the farm land of Moru people in Greater Mundri.
"In addtion to that, in so many forums dinka use to said the people of Greater Mundri stand for Federation and that is something not supported by the dinka and the regime in Juba.
"That is because dinka have tested the best of Moru land and they would wish to occupy it forceful if not now but in long run for their settlement."