i.e. is your own legal name in .com version a RIGHT?
no.
as with any other name, whether its a product, a place, a brand, a business name or whatever, trademark law will normally apply - names can be trademarked. try a search on the US patent office website for "leonardo dicaprio" (use the speech marks). [tess.uspto.gov...]
in general, you and the megastar and anyone else with the same name all have equal rights to the use of the name. however, the normal rules for trademarks will apply - prior use, passing off etc. trademark law is very complicated, so do some reading up on www.uspto.gov and make sure you use the name legitimately.
some basic and very rough guidance:
you may be waiving your rights to the domain name if you are not using it legitimately for yourself (ie, running a personal website or running a business website where the business has the same name as you etc etc). you must use the domain name legitimately (for yourself) and not to cash in on the name itself - that would be "passing off". you must also have prior use rights - if you were using it for a personal or business site prior to the megastar becoming famous, then great. but if not, and if the megastar has registered the name as a trademark, you could lose the domain. if you were/are using it as a personal site and have the rights to the name but now change it to a business site, trademark lawyers can say you are just cashing in on the domain (passing off) and you could lose your rights to the name.
do not take any of the above as legally correct or accurate etc - i'm tired after working all night again. check things yourself or go see a trademark lawyer. it looks like it doesn't cost very much to register a name as a trademark, so if it isn't registered already, get it registered.
>now change it to a business site, trademark lawyers can say you are just cashing in on the domain (passing off) and you could lose your rights to the name.
Agreed. One of the core rules of trademark is whether or not the use confuses the consumer. For instance, I hold a domain that is a resort area. It is also the trademark of a Fortune 500 apparel company. They sought to buy the domain, I refused. They then had their media agent seek ad placement on that domain. I refused again, citing the need to keep our "brands" from co-mingling. I will not even accept ads for local t-shirt companies on that domain. If you were to, say, put a poster affiliate link for this celebrity on your domain, I think it would put it in jeopardy.
that would be very generous of you to register the name and help the rich megastar get even richer, and also very generous of you to secure the domain name on behalf of the megastar. just don't expect any thanks or any compensation when you are forced to hand the domain name to them.