I think your concerns about the testimonies being misrepresented as "testimonies that were paid for" or "they were paid to say that" are valid. Perpetrators and those who disagree will often seize on any excuse to discredit victim testimony.
I am from Singapore Oral History Centre. In our guidelines, we never pay for any interviews. When payment is involved, there are many factors to consider, especially authenticity. Not only money, we do not give any other gift or reward either. However, in Asia's context, we do not go to visit people empty-handed. Thus our interviewers normally will bring some fruits or inexpensive item as a token for the first visit.
For those of you who use CONTENTdm (content management system) for oral history, you will be happy to see that UNC–Greensboro Special Collections recently launched their UNCG Institutional Memory Collection using OHMS and CONTENTdm. They even embedded the OHMS Viewer into the CDM interface. If you are using CDM and are interested in using OHMS, you should check this out: