>>PB.Net will create some dll.
>>Do you need to register this dll on client pc's ?
You wouldn't need to register the DLLs, but they and the runtime assemblies would need to be deployed to the client workstation.
>>Will this work with .Net Framework 2.0 or 4.0 ?
It's based on .Net 4.0
>>Is there an example available ?
No example specifically for MTOM. Lots for WCF in general.
>>Why it's not possible to transfer files bigger than 50 MB with webservices created in PB Classic?
Ran into that myself about 7 years to so. Had a case open with Sybase on it. It's so old I can't find it in the system anymore. I don't remember what the exact limit was, or what the exact reason was.
In my case, the web service we were calling allowed us to specify parameters to select subsets of data. I ended up creating dozens of smaller calls rather than the one big call to ensure that none of the smaller calls ended up trying to handle more data than PowerBuilder classic could support. That was a bit of a pain. However, the upside of that was that I was then able to invoke several calls simultaneously on different threads, which ended up greatly increasing the transfer rate.