I got the e-mail regarding this and when I tested the games in Chrome they ran out of sync, maybe because I have a 144Hz monitor.
I decided I wouldn't buy them. I think that if you pay a certain amount you get stand-alone versions (that run outside of a web browser), but I don't want to risk it. If I was sure that these were developed by Playmore/SNK and there were stand-along version that properly functioned, then I'd love to buy them, but I'm not currently very confident about that.
I did read that the ROMs were in thee games, so I guess if you bought it then you legally own the game. :D
Some people were saying that they would run in MAME, but if I've learned anything from MAME, it's that they could decided at any time that these ROMs weren't good enough. :)