Is it ok to have vaginal delivery after having two c-sections?

Yes. It can be. There is data to support vbac after two prior c sections. The chances of success are dependent on multiple factors such as the reason for the prior c sections and any history of prior vaginal birth. It is becoming difficult to find ob's willing to provide vbac so discuss it early. If this is an option you want, find a provider that will work with you.
Yes. You can try but only if you are an ideal candidate. It is important to review with your doctor the reason for each of your c-sections.
No. This is too complicated for a simple answer. The decision to vbac after two or even just one cesarean is a risk/benefit interplay between fetal and maternal benefit and risk. You should discuss the issue with your physician. Anyone that says it is either entirely safe or irresponsibly dangerous is being a bit unsophisticated about it.
No. Usually you will not find a physician comfortable with a trial of labor after 2 cesareans, but it is more likely if you had one or more vaginal births prior to having the 2 cesareans, or if you plan a very large family size. The policy varies from doctor to doctor and hospital to hospital, so be upfront and proactive if vbac (vaginal birth after cesarean) is something you would like to attempt.
Yes. More studies now confirm that if you have had "low transverse" incisions on the uterus (not the skin), then a routine delivery is "relatively safe." risks of uterine rupture (the c-section scar tearing during labor) can range from 1 - 5% -- but these are risks for you to discuss with your doctor to determine specifics for you.