One problem
One problem with a company making (and trying to sell) an HTML5/Javascript "program" is that the entire front-end (and possibly some of the backend) are public-viewable. "Open Source" in the truest sense: readily viewable code. Many companies from a closed-source world will likely do all they can to pull all their "special" functions back onto the server side of things and leave a skeleton of a front end to do input validation and drive the wiz-bang GUI. The great benefit I see from HTML5/Javascript is /more/ than just GUI is handled client-side. Why not do heavy computations and the like on the client? The only real use of the server-side would be data access control and collation. Once the requested data has been found, spit it out in pages (or as a whole, depending on your bandwidth/GUI model) and let the client expend resources to utilize it. However, to retain "company secrets" this will likely not happen where "GPL" isn't whispered. We'll end up with the same state we have today: glorified dumb terminals, with most of the compute power coming from servers and lots of server requests.