So much speculation...
Where to begin?
- Does it means Arca Noae can distribute/sell/build eComStation now?
No.
- Did Serenity Systems company was sold his company twice ? - I wish I can do that
...or it was not sold at the first place.
Serenity Systems International was never "sold." The development & marketing of eCS was handed off to/taken over by Mensys in 2007/2008 (I'm not exactly clear on the date, but surely a quick read of
this article should refresh everyone's recollections).
- So now Arca Noae has an agreement signed with Mensys/XEU? SSI has an agreement with Mensys, and SSI was bought by Arca Noae.
This has nothing to do with Mensys, XEU, or any other entity.
- Or is it eComStation out of the equation, since maybe only eCS was sold from SSI to Mensys?
This has nothing to do with eComStation (the product or brand name) directly. It does have to do with name recognition. People associate Serenity Systems with the refocus on OS/2 client development. That refocusing launched eComStation. Thus, people associate - to this day - Serenity Systems with eComStation, even though Serenity really had little or nothing to do with eComStation after 2007/2008.
- Or this does not apply to IBM's OEM agreement? or it applies?
Whatever arrangement Serenity had with IBM was long over by the time Arca Noae entered the space. Arca Noae did not inherit, acquire, or otherwise happen upon an agreement with IBM as a result of this transaction.
- Or maybe Arca Noae just bought SVISTA (http://en.wikipedia.org/wiki/SVISTA) and can return from the dead? 
As we know, SVISTA was - and continues to be - a sore spot for many of us involved in things at the time. The
Wikipedia article seems as complete a review as any (with references), to my recollection. Like eComStation and Serenity's license agreement with IBM, this product was long gone before Arca Noae was a figment in anyone's imagination.
Arca Noae's press release was entirely accurate: Whatever remained of the essence of Serenity Systems International is now part of Arca Noae. We did not acquire whatever original (or remaining) business entity there may have been. We look forward to being associated with the name of a company which is still so fondly remembered in our community.
Arca Noae continues to provide value to existing users of the platform. To that end, we are pursuing a number of other relationships with other people and companies, some well known and others less so. For reasons which should be obvious to even the casual observer, we cannot disclose all of our business details to outside parties, but we are happy to share good news when it comes our way. We view bringing serenity-systems.com under our wing as very good news. Please read the
Serenity Systems About page.