Bit of a n00b question is the PSP OS based on linux
PSP as in playstation portable

I'm not sure but it's extremely unlikely that the PSP is based on Linux, as the Linux kernel is licenced under the GPL. If Sony were to use it, they would have to release their source code.

The PSP firmware is based on completely proprietary software. The PSP has nothing to do with Linux. Even the PSP's primary drive, the UMD, is a completely proprietary, non-standard format.

In fact, the people at Sony have tried very hard to restrict the PSP firmware from all unauthorized access. Certain features of the PSP kernel have been completely removed or altered to make the PSP firmware unaccessible to non-authorized developers.

Of course, certain individuals have found ways around these limitations...

Also see the PSP-Linux project in Sourceforge. Seems kind of pointless, though.

And what about PS3?
I read it is based on Yellowdog distribution and Enlightement.
Could it be possible?