There're aren't any problems with this, it works fine.
However, I would only do this for personal use if I were you. The activity that FiberOptic mentioned has been discussed on the SunCobalt mailing lists (at great length some time ago after a large hosting provider was "caught" dong this) and it was made clear that Sun check for this and won't simply give you a telling off - apart from the fact that it's illegal and you'd be defrauding your customers.
Originally posted by danielbos Can i install my raq 3 with raq 4 os?
Thanks in advance,
Sun doesn't have a problem with anyone running the Raq 4 OS on a Raq 3 with a 300mhz. Processor. As long as it is described as such.
Sun will however get their "panties in a twist" is you market it as a Raq 4 just because it has the Raq 4 OS.
It's all in what you say and how you say it that they care about.